In vi you can operate on N chars, words, lines etc. quite efficiently. Mouse based editing, at least beyond what you see on the screen, is more laborious and less accurate. Typing a regexp to find or replace, or moving to a specific location in the file is still modal in a mode less editor.

I've never been a vi expert, but I've gone for long enough periods using vi keybindings to have been fluent with them. I think there is some kind of emotional/flow/mastery element - it just feels good to acquire these kinds of skills.

I don't use vi keybindings now for a number of reasons. Not using them hasn't slowed me down (which may not mean much either way). But I do see the appeal.

Comment 20671834 (by bakul) and 20671975 (by liability) make some good points. I also like vi. It is also why I made ZZTQED, being more modal than ZZT and KevEdit, and it also supports numeric command prefixes. I would also like it for TV/VCR, but, I have not seen such thing for a TV and VCR; many new ones don't even have numbered menus, and numbered menus are very advantageous.

I like [e]vi[l] because there is less to learn. In normal mode if you learn N movements and M actions, then you've actually learned N*M things, not N+M. That means a little bit of studying pays off huge.

Mode errors become easy to ignore at some point, but I actually noticed that I was definitely making a decent amount of mode errors for the first 2 years of my vi life.

I wouldn't be surprised if most people don't actually notice this, but I'm sure it happens.