many muds have/had those. there is intermud too. i guess ifmud just had the critical mass to keep people interested in communicating even though they stopped playing.
Chatting in the "Lounge" was always the starting point. The mud-building was what a few people did for kicks. ifMUD never had any systemic game play. The IF community has always had a strong core of people that interact daily. Some are on intfiction.org, some are elsewhere.