I guess that's partly because of a conflicting event: http://www.couchsurfing.com/group_read.html?gid=1059&post=1861916 (plus for me also diploma exam preps... otherwise I'd join also a whole lot more events in a heartbeat)
Oh, no, I will go to christine's party too! We can go all together afterwards! So we start to cook at 6, start to eat at about 7, will be finished at around 8 or later. Even if we're finished at 10 or 11, we will still be able to go!