As a vim user, I am 100% convinced that I am not that much faster than my colleagues who use normal key binds. However, I subjectively feel a lot less friction editing with vim keys than I do with the mouse and arrow keys. So Vim makes me happier...
To which I say, I've been using Vim (and nVim) for more than 20 years now, and the learning part is optional after a year or so of intense use.
Asking why people prefer vim is like asking why they prefer skateboard over rollers. You’re proficient at what you learned the most. The only thing you have to keep in mind is that every tool has its limits, so choose what you’re going learn from that perspective as well.