There is a sizable group of SF roleplayers who simplify their maps to the point of having two areas: starport and everywhere else. I'll admit that a lot of stuff starts and ends at starports. But this mentality also leads many people to think that systems put all their space traffic infra-structure in one location.
Nonsense in most cases.
I already made a case for outposts at nearby gas giants (for ships that want to gas and go but have other pressing needs.) Now I'm looking at the mainworld, the one that gets mentioned in the Atlas of the Imperium.
High Guard tells us that planetary navies may construct ships on their planet regardless of the existence of a shipyard using local resources which I could only take to mean that while a world might not have construction facilities for civilians it has other military facilities for building ships and projecting power. Note High Guard said 'ships' not craft so the military could build starships for itself even if the economy doesn't exist for civilian construction. t the very least we have separate civilian and military facilities.
A planet with Navy and Scout bases may have hundred or thousands of miles between them and the civilian port for security reasons. they don't have to be separated by a mere chainlink fence,
But getting back to the civilian facilities, time in money in business. That doesn't end merely when you touch down. That crate of err ... mining equipment (yeah mining equipment!) still needs to get from a port warehouse to your fortress ... errr mining fortress, mining camp! In a widely settled planet several hub cities might have their own starports to service local business at savings in time and money.
Megacorporations may also have their own ports (exclusively for their own ships thank you). When you blow a jump drive and the local port is only Type B and the Combine Shipping port is Type A that might be the time you're glad you got Forgery skill or Admin ("We''re here to hot ship a quark frakkalator to our Crystal Springs operation now! You were just stationed there and don't recognize us? See fellows I told you that misjump sent us back in time. Well at least we'll get there in record time, eh? Unhand me!! I am from the future!!) Your own port is also a great way to get a piece of almost everything being shipped locally.
Some starports might also have higher law levels than zero and be subject to local laws. A military operated starport would probably be a bad place to lug a PGMP around. Likewise landing at a military port due to misfortune might result in your ship being impounded for security reasons and you being subjected to questioning or worse. Landing at a megacorporation's field might be the same or worse, just done more quietly. What's one less free trader?
If a planet has orbital ports then the same considerations extend to them. It is possible different elements are specialized for greater efficiency or that the orbitals and the ground installations are under different management due to a power struggle or other politics. Land at one and the others won't accommodate you.
So you might have a non-industrial planet, a tidally locked one. On the sunlit face gems are mined and brought to the local port for sale. Meanwhile there's a trade in furs is going on at the arctic night side that's pretty brisk (see what I did there?) Another port is set up on the twilight terminator for tourism, government and military use. You can have three different ports with very different characters on the same planet (or spaceports YMMV). Military presence and customs is fairly loose at Nightport. Hunters need guns after all. Dayport has extensive repair facilities for mining equipment and might take a stab at repairing a ship's hull or structure thought the drives will likely require more sophisticated facilities. It also has the most stringent customs: jewels are easy to hide. Finally Grey Port has the most repair facilities and the largest commercial district.
A port might be 'full' when your intrepid merchant gets there. this will require you to land at another port or spend time chilling in orbit. The other port is not where your contract specifies delivery so an overland and over night trip is needed or you pay late fees. Oh and that customs official, the one you dated, is stationed at the full up port. So good luck getting that laser pistol through customs. Not to mention your cargo.
A size 8 plus world might have only one port with launch assistance for ships making less than 2 gees acceleration. Or each port might have their own methods. Sure Port Delta has the lowest berthing fees and launch fees but your ship has to ride the rocket sled. Port Alpha has the space tugs that gently lift you to orbit. It's way easier on the high passengers.
Some ports might have repulsor beams to lift ships or whole cargos into orbit. While repulsor beams in High Guard are fairly high tech level launch systems don't have to be. A repulsor defense system has to be able to hit a tiny missile at thousands of kilometers in the midst of a storm of ecm. A launch system has to lift a ship a few hundred kilometers and odds are the ship isn't dodging.
A couple of starports is also a great way to introduce people to the many cultures of a single planet. A balkanized world might have several starports with different capabilities each in the hands of different powers. This can lead to any number of dilemmas. Say you have a cargo of 'pharmaceuticals' that is highly illegal in the nation that controls the starport with the landing pits that your tail lander needs to ground safely. Similarly some planets may have safety concerns and require ships with certain drives to land at remote starports well away from cities or suburbs. Heading to town could be a couple of hours by air/raft.
The very diversity of starports in a subsector might be a spur for adventurer jobs. The TAS or a related organization might want to hire characters to rate them in a futuristic version of Yelp. Easy money till you try the little remote field with the incredible stores, entertainment and bistros.
That services the local pirate fleet.