I started learning vi around the same time, but in my case (since I was expecting to work on Unix systems for decades, which has proven true) it was "because it'll always be there." I.e. if you're SSHing into a server to fix a problem, it's possible that /usr/bin/emacs won't be there (perhaps the problem you're fixing is that /usr isn't mounting), but you can nearly always count on /bin/vi being available: if you can access the server at all, you will be able to access vi, so at least learn its basic keystrokes, our prof told us.

That advice was not entirely accurate (sometimes vi is in /usr/bin/vi, for example), and the merging of /bin with /usr/bin has made it kind of a moot point. (EDIT to add: Though the fact that busybox includes a basic vi implementation has kind of un-mooted the point, actually). But I first started learning vi because I figured I would need it professionally, and when the modal-editing workflow "clicked" for me, I figured out that I had just learned the editor I would want to stick with for years.

And although vim replaced vi and nvim replaced vim in my finger-macros, that has remained true to this day.