I have a neighbor who gets disability and for the life of me there is absolutely nothing wrong with her that I can tell. It turns out she hired a lawyer and expert witnesses and sued to prove she had fibromyalgia. She is one of the most active people I know and has never complained about any pain to me. I think she is simply gaming the system.
FWIW fibromyalgia is a real disorder, but crap like that is one reason people tend to believe it’s not.