Zero G
These are systems that you'd want to put in a non-rotating section of the space station. For smaller stations, you might be able to get away with just the actual center axle, but for larger stations, you'd want a large non-rotating section (let's call this a "drum"), and trains that speed people up to rotational speed to transfer between them.
Pressurized vs. Depressurized
This is a tech level consideration. For barely space age tech, you may not be shipping cargo around enough to make large open spaces useful. For Star Wars levels of advancement, your air lock is a forcefield, so you'll be able to move your entire ship into a pressurized space, making the point moot.
For those in between, having a hatch or gangway that people use to board and exit the space station can avoid requiring passengers to suit up, and can avoid lengthy delays while people cycle through air locks.
This is not always practical for large loads, and you may not even want to put them in a pressurized area. For that purpose, you'd want big areas of depressurized space close to where ships can dock
Docking
The most important role of the hub of a spinning space station is the docking complex. It provides a place for vehicles to attach without having to deal with centrifugal forces trying to throw the ship off. This is always best done right at the gravitational axis for smaller space stations. For stations where you might want more than two ships docked at once, you need a drum to manage all of the docks.
Trans-shipping Storage
As soon as you have space-based manufacturing, you have space based warehouses. This was done really well at Tycho station in The Expanse, where they had huge immobile volumes filled with trans-shipping containers that just stayed in one place. This is just a reasonable place to store goods coming off of a ship, while they wait for the outgoing ship to be available.
While there is undoubtably plenty of space to put this kind of thing outside of the station, you would want it to be close to where the cargo ships can connect to the station via a gantry. Higher value space would exist inside a Whipple shield to protect from micrometeorites.
Light manufacturing
Most manufacturing facilities would want to be on a separate station/platform where they aren't in the way of docking and transportation, but there will always be some cases where a finished good is best stored disassembled, and assembly is done as close to the location of use as possible.
Low-G areas
These are things for which a gravitational bias is beneficial for giving people something to push off on, or for keeping things sitting on a surface, but for which you don't really want full G of the outer sections.
Environmental systems
This is partially water storage, but also the systems that provide atmosphere for the rest of the station. Just like on Earth, you always want to store your water uphill so that it goes where you want it on its own.
Local warehousing
This would be a pressurized area where goods are stored after they've arrived, but before they're distributed. It would be full of small appliances and vehicles, building materials, furniture, and other things that are used up in the normal course of living. Pressurization makes it easy-access, and light gravity keeps things from floating away.
Groceries and sundries
Let's face it, it's easier to push around a shopping cart if you can push against the ground, and the cart doesn't weigh too much.
Athletics
You might want an area where the residents can do low-G obstacle courses and the equivalent of geriatric swimming.