Part One: Space Manufacturing.
Manufactering vacuum tubes?
Pumping air out to make a vacuum for vacuum tubes uses energy and costs money. Outer space provides a infinite amount of much thinner vacumn than can be produced on Earth. If vacuum tubes are sturdy enough to survive passage down to a planetary surface, and other factors are favorable, manufactoring them on a space station could be profitable.
Outer space is a good place for manufacturing anything which requires a vacuum and/or microgravity and maybe also the ability to change the level of gravity during manufacture by rising or lowering the machinery toward or away fromt the center of the rotating space habitat.
Maybe airtight gas bags (or vacuum bags) of airships could be made in outer space. They could have electomagnets in the fabic. They can be exposed to vacuum and lose all their air, and them be folded up and shipped to a planet with an atmopshere. There they can be installed inside airships with atomic power supply. When the power supply is hooked up to the gas bags it powers the electomagnets in the gas bags which al lhave the same charge and so repell each other. Thus the gas bags expand to fill the ineterior and slowly push out all the air from inside the airship. When the interior is completely filled with vacuum filled bags the air vents can be closed.
The step of making the bags in outer space would ensre that there would as hard a vacuum as possible insdide them. And vacuum is even lighter than hydrogen gas and so has more lifting power.
Possibly giant vacuum bags could be used to support colonies floating in the atmospheres of gas giant planets.
And I suppsoe there are lot of other things which people can imagine might be manufactured only in space, or better in space.
Part Two. Space Tourism.
Space tourism is a industry which is just sort of taking off on (from) Earth.
People usually imagine space habitats as giant hollow spinning cylinders filled with air and with about one Earth gravity (1 g) on the inside of the outer cylinder walls. And they imagine that the inside will be one giant void filled with air.
And that seems like a great waste of space and air to me. I imagine that a real space habitat should have several inhabited levels one above the other, like an underground city with several levels, at about the distance necessary for 1 g.
And above those several underground levels there can be an open space like is usually pictured. But not wastefully filling the whole interior above. Instead there will be a roof over that air filled "exterior" space, probablly just a few whundred feet above the "ground" level, a cylinder running all the way around the habitat and supported by columns from below and/or suspended by wires from the center of the cylinder.
And there would be a vacuum above the roof of that open air section.
And somewhere above that roof there would another pair of concentric air tight cylnders with breathable atmosphere. The gravity level on the bottom cylinder in that pair should be about 1.352 meters per second per second or 0.138 g, the surface gravity of Titan. It is claimed that people would be able to strap artifical wings on their arms and fly in the low surface gravity and dense atmosphere of Titan.
So people should be able to take off from the surface and fly higher in regions of even lower gravity in the air filled space between the two cylinders. Writers have imagned people flying with wings strapped to their arms in the vast interior space of O'Neil cylinders. And of course if such flyers get too low and too close to the 1 g level. the gravity will be two strong for them to fly back up and they plummet to their deaths.
So with my design the natives can tell the tourists that they thought of everything and the flying area has been designed to avoid that danger and be perfectly safe. And then a clever enough writer should be able to imagine a way for a dumb enough tourist or a lazy designer of the habitat to find or make a falling danger, and also think of a way to save the endangered person.
And no doubt there are other space tourism features which could be imagined.
I note that a section of the habitat projecting out and down from the 1 g level might be visited by tourists to experience higher gavity. It is quite possible that spending specific periods of time at specific levels of gravity slightly higher than 1 g might be discovered to beneficial for one's health.
Part Three: A Space Graveyard.
Possibly one industry in the space habitat would be storing "corpsicles", dead people frozen in the hope of being brought back to life by the advanced science of future centuries.
In popular culture the forzen dead are depicted as stored in mechanical refrigerator units, but vats of liquid nitrogen are actually used on Earth.
In outer space a volume of vacuum completely enclosed and thus shaded from sunlight should have a very temperature, and so "corpsicles" within it should maintain a steady low temperature. And cleaver designs to make certain the volume within stays within the correct temperatue range through absolutely passive means no matter what happens might be imagined.
Part Four: Port Facilities.
Supplies coming from outer space or from a planetary surface to the space station or habitat to be used there will have to be unloaded in some sort of port facilities. People coming and going will have to use some sort of port facilities.
Thus your space station or space habitat will have some sort of docking or port facilities for its own use. And it may have larger port facilities for commercial use. And as others have pointed, surface to orbit space ships, interplanetary cargo ships and passenger liners, and interstellar cargo and passenger ships might have very different structural requirements and different types of ships might be needed for thoe different purposes.
Thus some sort of port facilities in orbit around planets or floating in interplanetary or interstellar space may be needed in the space travel system of a story.
So science fiction writers have been imagining the use of space stations and space habitats as busy space ports for many decades before Babylon 5 (1993-1998) or Star Trek: Deep Space Nine (1993-1999). Thus making a fictional Ctesiphon Seven or Back Space Ten a space port is very logical.
