Different Kinds of Space Ships
There are different types of spaceships, the same way there are different types of transport in the real world. You can walk, cycle, drive, get a train or bus, or go to the airport. You can in principle get an airplane to the shops or to work. But this is rare for practical and cost reasons. And the few people who do commute by train still use other transportation to get from the airport to their workplace. The plane won't drop them off t the door.
There are different types of spaceships for different jobs. The spaceships that move from one orbital habitat to another cannot take off or land from the surface. The kind that go from the surface to orbit cannot move long distances between planets.
We could in principle build a ship that does both. But it would be a waste to lug all that surface-to-orbit gear around between planets. Plus that gear was expensive, and it being idle when the ship is in space is lost opportunity cost. That's like having an airplane full of bicycles. They are not doing anything when the plane is in the air.