Mostly for Org-mode. Even though modern editors and lightweight alternatives handle daily coding smoothly, Org-mode's plain-text outlining, agenda management, and workflow structure are still hard to fully replace anywhere else.
Why would I use something inferior to emacs in the first place? :)
I use Emacs for everything ;) Other tools just feel wrong, to be honest. I am so accustomed to my handcrafted environment I have created in Emacs!