I remember one of my characters got a ring of three wishes once. lol. I think we just didn't assume that anything much above name level really existed in the PC world. There were a few super high level 'retired' PCs that one of my friends and his other group ended up with, but we treated them as sort of just rumors or legends, you never actually met them in any of our games, we just didn't assume things like 20th level PCs really existed.
So, for us anyway, wishing for higher stats wasn't much of a thing. You could of course try it, in a rare case, but IIRC the rule was basically you got 1 point per wish, and then after 16 you got 0.1 points per wish, or something like that. Nobody ever found 10 wishes AFAIK, or if they did they weren't saying. lol. Just slightly different versions of 'high level'. I'm pretty my 14th level wizard was about the pinnacle of PCs in our game. Mike, the GM, definitely had a lot of bad guys gunning for him.