Why? IRCnet has been around for such a long time that it came before the idea of channel services and nick name services.

With services, you have restrictions. Political situations among the administration of a network also make change difficult. Imagine the task of implimenting services on a huge preexisting network that has never had them before.

For a more in depth write up on this subject, check out http://www.irchelp.org/irchelp/networks/noserv.html