Vi's learning curve is very steep too. As an emacs user, I sometimes use vi when pairing with a vi colleague. I've tried to learn some more advanced vi functionalities, but I always think the learning curve is not worth leaving emacs behind.

I'm thinking that the issue is rather that when you learn your first editor (emacs or vi), you don't have other good text editors as reference so you swallow the learning curve and keep pushing. When learning the second one, its harder to justify the learning effort.