Simple. I don't know emacs that well :) I didn't even know emacs had a terminal mode until I looked this up; my main experience with emacs was when I was writing prolog and the IDE was emacs based. I didn't find it as nice to use back then so I never gave it a serious shot.

By comparison nano is everywhere and was super-simple to configure and spruce-up with custom functions, so it just stuck with me.

As for other competitors, when comparing to vim, I find it much simpler to use, and to the surprise of most vim users I speak to, equally powerful (at least for my needs).