Someone recovering from hand surgery may need full keyboard or voice-control access for weeks without ever having used those tools before; someone recovering from eye surgery may temporarily need high contrast and large text the same way a person with permanent low vision does. Because the barriers involved are often functionally identical to those faced by people with permanent disabilities, building for permanent disability in the first place already covers most temporary disability needs too.
This overlap is a useful reminder that accessible design is not a narrow feature for a fixed, small population, but something nearly everyone will rely on at some point in their life, even if only briefly.