Because I don't choose what tools are available on every server at work, and it's guaranteed that at the very least old-school vi is installed on every linux server, and often vim. Maintaining that muscle memory is useful.

I'll field this one as someone who has used regular ol' Vim for ~18 years and never switched. Why switch if your tool is working fine? I use vim literally every day all day long and it does everything I need it to do. Switching has a cost and there's no reason to pay it if it's working fine.

I use both gvim on linux and macvim on mac for a lot of things--not 'real' coding, typically, but opening and editing scripts and config files, writing in markdown, etc; I'm usually opening these from dolphin or finder. In the terminal, working on real code bases and not scripts, I use neovim. My configs for these have diverged a bit over the years but since the use cases are different, it doesn't bother me.

I didn't switch because there was no reason to. And there is still none.

One reason might be how off-putting the Neovim community is, hijacking Vim discussions to denigrate an all-time-great, beloved work of technology and its creator (who did decades of work for free, gave it to the world, and gave any money to actual orphans) all for Neovim users'/devs' own egos, promotion, and obsession. Almost all of Neovim was made by Moolenaar, from concept to execution, and I don't know that I've ever seen any gratitude.

I've never seen Vim users do that. If I had to choose, I'd use Vim.

gvim?

muscle memory mainly, I guess?

Sure, switching might not be that troublesome, but I can tell you the first 48 hours or so will be painful, you'll insert stray ":" and "i" characters everywhere :)