Sure, and so is Xeyes and ed, but that doesn't mean many people use it. I might use xterm on a remote system I vnc into that has no desktop manager but other than that I'm generally running everything in my local terminal emulator (and then often also in tmux).

I'm sure I have xterm installed but I have never run it locally since like probably most people I just use the terminal emulator for my desktop environment.

Yes, but despite vim being there on tons of systems, nobody except vim users ever run it.

Same for xterm. It's terrible and almost nobody uses it.