Goddammit I forgot AIM, that was the other one. So by the time jabber and xmpp came around there were giant existing networks: AIM, ICQ, Messenger. Obviously n

Goddammit I forgot AIM, that was the other one. So by the time jabber and xmpp came around there were giant existing networks: AIM, ICQ, Messenger. Obviously none of them had any business reason to adopt an open, etc protocol. Additionally even if they wanted to, actually doing it would likely have been a significant engineering challenge, due to the need to maintain compatibility between client versions.