AIBU to think that if you are a host and there are people in the room who don't know each other, it's your duty to introduce them?
I have been in a fair few situations in the last few years (house parties, children's parties with parents present, evening class type things) where no introductions were done. I find it really awkward, standing around not knowing everyone else's name. I always make a point of introducing myself and, if I'm "host," of introducing everyone who might not know each other. IMO it makes everything much more sociable. It immediately breaks the ice and gets people talking. In fact, I hosted a big party years ago involving many unconnected friends and many of them became friends at that event and are still friends to this day.
Am I odd? It seems very few other people do introductions.