Craftsmen and tools. It is an age old story, you grow to trust and understand a tool. Programmers and text editors are an extreme example, because programmers often spend 30+ hours a week using a single too, their editor.

Vim and Emacs have survived because they are "fit for a purpose"... they are really good at editing text! Emacs has a niche in expandability. You can always twist Emacs to do your bidding... and it has a culture of tinkers. Vim has much more of a culture of users, people who want to edit text rather that toy with their editor.

These editors have roots in the 70s and are still kicking -- that isn't some random accident, that is because the fundamental act of editing text hasn't change too much.