To be completely fair, it's not like they are going to remotely delete it or anything, the current version which I like functions, and has no glaring bugs, and will continue to function.
And if I did use emacs, and somehow it changed in a way that I hated, I really doubt I'd have the time to fix it. Work isn't going to pay me to sit around and write my own text editor.
I see your point. One day I'm going to write a guide to choosing your editor, or your trusty tools, for that matter. There are further advantages in choosing an open-source established editor.
It all boils down to a trade-off. As long as you don't invest too much time into learning a tool, you don't mind losing your investment. Recently I have switched to Opera as my default browser. I couldn't stand Firefox anymore, Chrome didn't suit me. Opera is proprietary and closed-source, but then I'm not going to dig too much into its internals.
And if I did use emacs, and somehow it changed in a way that I hated, I really doubt I'd have the time to fix it. Work isn't going to pay me to sit around and write my own text editor.