So, out in Den, Colorado, population 2,600, the local abandoned prison had just been taken over by the Slavers Guild. The Slavers Guild has a huge advantage, technologically, over most other natives of Colorado. Weaponry. Most inhabitants of Den use either bows and arrows, or machetes, as their primary weapons. But the Slavers, they have imported weapons like AK-47s, and the Slavers Guild Base even has a mounted artillery gun. These Slavers have clients stretching from Kansas to Nevada, and logically, a town of 2,600 potential slaves would be helpful. So, why might the Slavers not use their technology to take over Den?
If the slavers took over Den, then they wouldn't be able to trade locally for food anymore. They'd have to grow their own food.
If the slavers take over Den, then they can't sell their product to the citizens of Den.
As a general rule, you don't want to own slaves in a place where the slaves know more about the area than you do. So if they did enslave the populace, they would then have to move everyone to other areas. But then who would grow the food? They'd have to import other slaves to grow food locally. It's simply easier to keep things the way that they are.
It's also worth noting that while an AK-47 is clearly superior to a bow and arrow in a stand up fight, the bow is the superior guerilla weapon. It is quiet and easy to keep supplied with ammunition. The locals could fade into the wilderness and watch for small bands of slavers roaming outside the town. A regular pattern of ambush would mean that the slavers would only be able to move around in large groups. Meanwhile, the locals could sabotage the roads and even production facilities.
It is much safer for the slavers to raid at a distance. They move in, get their captives, and leave. Because they work with the citizens of Den, the slavers will get help from the local populace when the freedom fighters track them down and attack. And the slavers will have the advantage of local knowledge of the area.
It's not economical to do so.
You indicate that the slavers import their weapons. That implies that they can't produce them on their own: either they don't know how, or they don't have the equipment or resources to do so. Whichever it is, their advanced weapons are a precious asset that should not be wasted. Manpower is also a consideration - if they get into a pitched battle against Den, even with assault rifles against bows they're liable to take losses. If it gets down to house-by-house clearance, they will certainly take losses; they might even lose more than the natives. And if there's any fighting, there's a chance some of their weapons will be lost, captured, or stolen.
They also won't be able to make use of the whole population. Many of the residents will be too young, too old, too weak or sickly, and that's without considering anyone injured or killed in capturing the town. (Assault rifles are great at killing people, but they're not great at injuring them in ways that leave useful slaves behind.)
Finally, there are probably much more lucrative places to pick up slaves. A mid-sized community has the ability and more importantly the will to defend itself; smaller towns, travelers, other outlaw groups, and the like don't. Like any business, the slavers will gravitate towards sure things.
I can think of a few good reasons.
Governments do not look kindly on this kind of thing
Governments tend to frown upon people doing things that could threaten their power. Why? Because history is replete with governments that ignored some threat to their hegemony and were ultimately overthrown by it.
This slavers' guild is a guild. The question in fact specifies they're not the government. So if they did anything like this, every nearby government is going to be thinking about their new neighbors. What are their new neighbors likely to do? Well, consider the situation:
- The Slavers just became a government by conquest
- Which clearly is a hostile, expansionist government
- Who took something because it was easy pickings and for no other reason
- And just conquered one of my neighbors
The conclusion is obvious. The slavers' guild is a threat. Take them out now, while they're a small threat. Don't pussyfoot around and just take out the new government of Den, Colorado. You can't trust the leadership of the Slavers' Guild as a whole not to try this again.
Squashing small threats is easy. Do nothing, and it may grow big enough to take you out. So the neighboring armies will roll right over Den, Colorado... And just keep going, taking out every Slavers Guild in their lands. The guild is likely dissolved, its leaders dead or in jail.
Running the government is a lot of bother
These folks are the Slavers Guild. They're good at things related to that. They make a lot of money doing it. Now they need to take over governmental functions. Those are a royal pain in the neck, and they cost a lot of money too. If the Slavers Guild wanted to do these things, they'd already be doing them. The guild almost certainly makes more money sticking to what it's good at doing.
Even a Slavers Guild has a reputation to maintain
For one thing, ordinary people need to know that they are safe from the Slavers Guild in most circumstances, or they'll never tolerate its existence. If I walk into the Slavers Guild to buy a slave, I need to be sure they won't decide they can get more money out of me by threatening to enslave me if I don't pay them off. If I'm a government, I need to know that they're not going to ruin my economy by absconding with the people that generate all my tax revenue. Or cause riots by sending out squads to enslave people that wander too close to Slaver Guildhall.
In other words, any guild old and successful enough to become known as "The" Slavers Guild will have rules specifically enumerating exactly who is, and is not, a slave and under exactly what circumstances they can take someone. Guilds write bylaws to ensure they can ply their trade in peace, without pissing off the government or enough of their fellow countrymen to cause trouble. And said rules definitely will prohibit the Slavers Guild from enslaving people simply because they can. Guild members caught violating these rules will absolutely get in a lot of trouble.
Slavery is predatory behaviour by the strong against the weak. The Arab slave traders would buy captives from African tribes from their intertribal wars and sell them to the highest bidders (after 1500, the Europeans were willing to pay much more for servile labour than other African tribes).
But the slavers still needed to be vary wary that the hundreds of slaves packed in the holds would not be able to rise up and kill the crews. Slave owners in the Caribbean and America were always worried about the possibility of a slave revolt.
Even earlier in history, the Spartans ruled over the Helots in the area around the territories of Laconia. The rise of the Spartan military state was mostly in response to the possibility the more numerous Helots would rise up and overthrow their rulers, indeed some Greeks in other city states characterized the hatred of the Helots as being so great they "would eat the Spartans raw" if given the opportunity.
So the Slavers guild may have military superiority over the citizens of the city, but realize that attempting to actually enslave them would embroil them in a never ending conflict, and even "winning" would mean they would essentially be trapped inside their fortress and sleeping with one eye open in case of a slave revolt. They might also fear that potential enemies would stoke the fires of a slave revolt, or use the slaves to overthrow their power (in ancient history, the City State of Thebes did march on Laconia and after overawing the Spartans, marched through the countryside and freed the Helots, building large fortified cities like Megalopolis to allow the Helots to resist any future attempts by the Spartans to reconquer the area. Sparta's decline as a Great Power in the ancient world is directly tied to the loss of their slaves and the farmlands the slaves cultivated for the Spartan economy).
So the short answer is while the slavers may be technically able to conquer the city, the long term price will be far greater than any benefits they may gain from doing so.
Arrows can be collected and reused but modern bullets might be extremely hard to come by. The guns are great to show off and to use to make an example of people who resist them but they simply don't have the reserves to try and rule the place.
As a result they like to show their fire power and show disdain for controlling the whole area because they know they will lose if it comes to open warfare but the other people don't know this.
Here's another possibility: family ties.
Perhaps the leadership of the Slavers are all from Den (or maybe just the top leader), and their family (parents, siblings, aunts, uncles, cousins, etc.) still live in the area. With a population of only 2500, especially in a time when mobility is limited (e.g no cars), it's not unlikely that someone could be related to a significant percentage of that population.
If you are in a forest, climb on the tallest tree and start bumping your fists on your mighty chest, you are making a statement of power. It will scare the weaklings and will attract the attention of the daring ones, who will get a good preparation before making their move on you.
If your goal is to attract attention, you can do it. It will require that you devote a good part of your energies and resources to be prepared. If you want to stay under the radar and devote your energies to something else, you simply don't climb the tree. You are still strong, but your opponent will notice only if they attack you. And I guess when you have AK47 it makes a huge difference if your attacker is expecting stick and stones instead of bullets.
The world you describe looks like a world where living undercover is to be preferred, so it makes sense that no showoff is done.