If I'm not present when friends are chatting I don't get to replay what they were saying before I arrived, or after I leave.
I think that is the fundamental disjoint - features are attributed to IRC that were not intended, and then attempts to bolt them on through services, bouncers, or whatever, is never going to create a seamless rich experience that many seem to want.
For me, IRC has always been the avenue for mostly throwaway, real-time at-this-moment off-the-top-of-my-head stream-of-consciousness discussion, with Usenet or forums and email mailing lists for more long-running considered and logged discussions.
I've never been impressed or attracted to products that try to force the two styles together.