Yep what tdogg said. Some of the local ones are "useful" if you will. I'm not a member of an actual club here (I play as many different courses as I can every year) so if I want a GHIN handicap I need to join a type 3 and our local RDGA offers that. They also put on local tournaments and support the local golf community.
But otherwise I don't get anything from the USGA (outside of trinkets) but I think it's important to be a member to support them as I can.