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 used to think this too, but I routinely switch back and forth between neovim and vim now for close to a decade, and I've never noticed. In fact I often don't even notice which one I'm using unless I explicitly check. Once you add neovim-only plugins that can change of course, but if you can't choose what tools are available on the server then I would imagine you're not installing plugins anyway.
