Seinfeld is a jerk with his sneering “joke” about people on carts, but there is a grain of truth there. It’s not as though the airlines are asking for proof of disability, and just like service animals, that means widespread abuse of the system is a certainty. I recall there was a prior thread in which @LSLGuy commented that the miraculous healing power of air travel is a well known phenomenon in the industry. On virtually every flight, a significant proportion the wheelchairs waiting at the destination (the same number as those requested for boarding) are not used.
ETA here:
Indians and airport wheelchairs - #9 by LSLGuy
(nothing to do with the “Indians” aspect of the OP)