I think stations can be self-sustaining, but they have to be much, much larger than the ISS.

But the bigger issue is, what functions would you even want in LEO that would help? I guess a beanstalk top would be really helpful, but it's hard to see anything that wipes out Earth being unable to take down the beanstalk too, unless it was a plague and the stalk had very impressive passive safety features.

Having other satellites, like GPS, and surveys, and so forth, could be really helpful, but that's not a space station.

It would make a good rendezvous point so you can have shuttles and ships, and the ships don't need to hang out all the time. It would make things cheaper and faster, though not make something possible that otherwise wouldn't be.

I guess a facility for checking out and repairing atmospheric entry vehicles would be very handy if there's any concern about that.