Apples and oranges. IRC is in general used for group-chat with topic channels, while other IM protocols (such as XMPP, ICQ, Skype, MSN, AIM, ...) are primarily

Apples and oranges. IRC is in general used for group-chat with topic channels, while other IM protocols (such as XMPP, ICQ, Skype, MSN, AIM, ...) are primarily 1:1 chats with friend/buddy lists. That said, XMPP MUC (multi-user chat) is terrible, overengineered and less usable than IRC is. (Disclaimer: I hacked on bits and pieces of XMPP client in Telepathy).