A 5 second startup time for a text editor is extremely annoying when all you want to do is, say, type some small commit message.
For remote files there's tramp.
But, I do agree that any sysadmin should know enough basic vi[m] to get around, because vi is almost always available on any unix system. Emacs (or nano) might not be installed.
That said, though, if I was accustomed to one of my primary tools taking a half-second to start, I think I'd miss it pretty bad if it went away.
Just the fact that people on both sides (glibc and emacs) are treating this so seriously seems to indicate a rather admirable dedication to keeping the quality of the software as high as possible.
Also, if I'm screwing with my .emacs it's nice to have instant feedback beyond eval'ing any changes I make as I go.