as the others have stated, the list of reasons is long. But it can also change.
I remember a club member who started exercising after a cardiac event because he ‘had to’. When I first met him, he had become a fixture because he was there almost every day. He told me: “That heart attack was the best thing that ever happened to me. Because of it, I started exercising, and I now feel better than at any point in my life before.”
I wished there were more people like him ……