Many people may be able to get up the wheelchair and walk a little, but may not be able to walk a mile in the airport... Or may not be able to navigate the complicated airport environment.
Exactly. And not all disabilities are visible either.
I was just replying to someone saying that there is animosity towards disabled people ("people question why they needed a chair. They had people call them wheels in public..."). I haven't heard or seen it verbalized explicitly, with that one exception of airports, where people publicly mumble and mention it. I don't like to see it and I don't support that but that's what people do.