Emacs user here for nearly 17 years now, Spacemacs user for about a year and a half. I'm an Emacs user, because it is the most powerful, most customisable thing, ever. It's not just a text editor, it is an IDE, an IRC client, an Email and RSS feed reader, a music player, and whatever else you can imagine. I live inside Emacs. The only thing I do outside of it, is browsing.
This way, I have all the familiar key bindings, and the full power of Emacs at my fingertips, no matter what I do. It is consistent, powerful, and doesn't care that I have thousands of buffers open. Being able to reach everything, from anywhere, pretty much effortlessly, is an incredible boost to both productivity, and comfort.