Why do I still use the emacs text editor after all these years? I could try explaining it to you, but I think I’ll defer this one to science fiction author Neal Stephenson:
I use emacs, which might be thought of as a thermonuclear word processor. It was created by Richard Stallman; enough said. It is written in Lisp, which is the only computer language that is beautiful. It is colossal, and yet it only edits straight ASCII text files, which is to say, no fonts, no boldface, no underlining. In other words, the engineer-hours that, in the case of Microsoft Word, were devoted to features like mail merge, and the ability to embed feature-length motion pictures in corporate memoranda, were, in the case of emacs, focused with maniacal intensity on the deceptively simple-seeming problem of editing text. If you are a professional writer—i.e., if someone else is getting paid to worry about how your words are formatted and printed—emacs outshines all other editing software in approximately the same way that the noonday sun does the stars. It is not just bigger and brighter; it simply makes everything else vanish.
In short, I use emacs because every other editor I’ve tried only offers a different subset of the features I get from this old editor. Until something better comes along, I’ll be happily M-x editing programs away.