Because it is full-featured editor running fully in text mode (so you can run it on the remote server or over a serial line) and uses short commands for most text edit needs. In comparison nano provides only very basic feaures (like Notepad) and emacs (according to Stallman) is like an operating system with more complicated keyboard shortcuts. Of course you can run VisualStudio Code over VPN but that would waste too much network traffic and the input would lag more.