But they were familiar enough with vines then leather cord then ribbing and so on.

We of course are not talking about today, we're talking about thousands of years ago, and a whole series of comfortably familiar skeuomorphic transitions. Until by now, knife handles have the obviousness they have through that heritage of iterative familiarity.

Such isn't an opinion, it's researched if you look. (Not that this user would know, of course.)