Considering how emacs is very old (lots of person decades of development), is focused on niche/advanced text editing, and is built around one of the most praised languages, it's interesting that it doesn't have this.

SubEthaEdit's use of bonjour to fing other computers on the LAN running it is a great advantage. Heck, even MS OneNote has a collaborative edit feature if you give the hostbnames/IPs.