There's also the fact that D&D was designed with player retirement assumed at Name level. (Sort of)Well, the idea that most games are going to just have the same challenges at high-experience play as low doesn't seem supported in much of any game, in or out of the D&D sphere. The only reason it wasn't much of an issue prior to 3e is that there wasn't a full blown skill system, but it wasn't like saves and AC didn't tend to go up on opposition, so...

AD&D 1E especially starts struggling at higher levels. And it slows down PC progressions significantly at that point.
Early AD&D 1E looks very much like bounded accuracy - with very, very few exceptions, monster ACs go from 0 to 9. (The exceptions are mostly demons and devils - otherwise known as monsters introduced in the OD&D supplement Eldritch Wizardry).
Cheers,
Merric