Second: in physical space: ramps are required to be implemented in a way that supports wheelchair use. Yet they create alternative affordances: I have appreciated them when when I have broken a limb, for example, even though they weren’t “intended” for that. They are clearly mostly used by delivery people; not only does it make deliveries easier, but reduces incidents of injuries, strains etc.
The same applies to web sites: cleaner affordances allow people to use the page in ways not imagined by the designer.
* By imperfectly I don’t mean “not hyper vigilantly”, I mean that it is often observed in the breach; sometimes it can have negative effects (consider the Berkeley videos case), etc. But that is much better than no attempt at all.