If you are rooted, you do no need a wire to bootstrap, there are apps that start the process, but it's mainly for convinience.

Also this lets you run script on your real device instead of the chroot thing of termux which can be helpful (e.g. accessing /data/data stuff which is a pain with termux, not sure if its even possible).

And my last reason is just that why would I need a separate app that I need to configure when I can just have a real ssh server