Permanent presence
NASA is not a commercial society, so it won't be able to sell the space station.
The Space station doesn't even belong to a specific agency as it is an international project.
If NASA wants to do anything that requires a long duration mission (Moon base or trip to Mars), then it must one way or another start with the space station. It's there, in space, and astronauts could stay months up there. Much longer than they do now.