Atto's default key bindings match Emacs, which is about as standard as you get for non-modal editing keys in older Unix traditions.
WordStar was for CP/M and MS-DOS, which was very much doing its own thing. Atto is for Unix.
For many, it is indeed about what they call "muscle memory". Almost impossible to change after so many years. And therefore I hope everyone would provide keybinding alternatives generally (shouldn't be that hard).
Despite all those flaws, people keep writing new software in C every day, go figure.
Or ARM? It's from the 1980s! So old!