Which does beg the question why the others haven’t implemented such functionality (yet)?
Helix continues the work previously done by Kakoune (some people prefer Kakoune over Helix anyway). As to why - because it, like any other computer science topic, is a topic of active research, and Kakoune is the next generation of research into modal editing. Disclaimer: I use Neovim because it works well enough for me (it does offer more configurability, but I doubt I use it that much) and I don’t want to learn another set of hotkeys (which is similar enough, but still different).
I shouldn’t expect remote accessing some random server will allow me to use Helix, right?
That’s right, but as a Neovim user, it’s hard for me to use Vi, because it lacks many features, and I don’t know which ones. When you start going from basic to advanced knowledge, it sadly doesn’t translate. Of course, I would still pick Vi over Nano any day.
There’s a similar problem with many shells (fish, readline (bash)) that don’t fully implement Vim’s features, so their Vi mode sucks, but I still use it.