We look at action movies for rationalization. John McClane, Indiana Jones, Rambo etc get punched, kicked, shot, stabbed, blown up, thrown out of moving vehicles etc and somehow manage to survive stuff that unnamed mooks die from instantly.
As I prefaced, at OUR table, it works. We don't apply "realism" or "physics" when it comes to this stuff. We accept that D&D PCs are basically super heroes and leave it at that.
It actually causes LESS confusion. For US. For most of the hobby, I agree with you, it's handwaved and ignored as "one of those wacky sacred cows of D&D".
In other RPGs, which have less ambiguous health trackers, we go with the flow.
edit: it's also a bit like video games. In plenty of genres, from the gritty to the most super heroic, the protagonist gradually is able to take more and more stab wounds, gun shots, animal bites than at the beginning of the game. There's no ambiguity: there's blood splatters. We just extend the same thing to D&D, also a game.