Among my niece and her friends if
you are invited to a party
you come and maybe bring a date you but don't just bring a random group of people with you. It isn't like "Hey, party on Elm street everyone is invited". Or like Open Houses. I'm not sure if parties in general are just smaller or maybe people don't give them as often. Or maybe, for safety reasons women are more careful who they invite into their apartment (not a friend of a friend of a friend who just heard about the party).
Maybe "singles parties" are more for people in the 30s, or in big cities like on Sex in the City.
My niece is pretty knowledgable and she and a friend or two that she asked
had never even heard of the concept.