First of all, "technicals" are any non-standard vehicles, most often civilian vehicles, that are converted to light fighting vehicles. This can be anything from a car that carries infantry to battle to trucks with artillery or anti-tank canons mounted on top. So while the Toyota war has given us the idea that a technical is a weaponized pickup truck it is actually broader than that.
Technicals are in use in Russia for example as support squads. I'll be using "technical" for a variety of civilian vehicles repurposed for warfare, from ordinary cars to trucks. Lets put some things in a row:
- technicals are relatively cheap to buy compared to armored vehicles.
- depending on how much armor you strap on they can be very fuel efficient
- technicals use similar skills to operate and maintain that is already found in much of the population. Similar to how half-tracks were a solution in WWII to reduce the training time required for skilled drivers and maintenance personell of their military vehicles.
- the production capacity for such vehicles is much much higher than other armored vehicles. Like in WWII, any current factory can be repurposed to build such vehicles while modern armored vehicle production is highly specialized and not easy to shift to civilian production facilities.
- it is easy to supply and maintain such vehicles. No specialized fuels or equipment is necessary. A pickup with a crane pulling a cart with supplies could be used to maintain several vehicles at a time, and when necessary any cardealer and workshop garage can repair the vehicles as well, assuming parts are available.
- a russian manual mentioned in an ascending list that small-arms proof armor is deemed heavier than protection against shrapnel, although I assume shrapnel of "small" explosives is meant rather than a large artillery shell. That means they can be lightly armored.
- technicals have the best use in maneuver warfare, where they can be effective even against tanks. They also have roles as infantry support platforms where having one with you is superior to not having one, especially when it comes mounted with heavy machine guns, mortars or other powerful support weapons.
With that in mind such vehicles could be used in an extended war of attrition similar to WWII. After most costly and hard to produce cruise missiles, JDAM's and other munitions are depleted while access to the wide variety of required resources are cut or limited, you are going to need cheap and easier to produce vehicles.
The French for example had great success with an armored car mounted with a variety if weapons including a 90mm canon (the Panhard series). Which due to it being purposefully produced no longer counts as a technical but it is an indication of the potential that technicals can have.
While your (remaining) main forces create frontlines and area's that can't be easily penetrated your army of technicals and motorcycles will engage in maneuver warfare. They use their speed and mobility to pass through any opening in the frontline, such as after your forces have attacked the enemy frontlines. Then they seek out the vitals of an army: supply lines, command and control centers, communication equipment, radars, anti-aircraft sites, depots, specialist personell such as those that maintain tanks and perhaps even daring raids at production facilities before returning, possibly destroying their own vehicles when they run out of ammo and gas before receiving new sets of vehicles.
Otherwise such vehicles could simply create mechanized infantry regiments from regular infantry. The added mobility and firepower is useful at most points in time, especially if your armies are restricted by resources in the amount of advanced vehicles and weapons they can create.