I joined USSailing 2 or three years ago because I thought I was going to race in an Alter Cup qualifier- which I didn't end up doing anyway. I got the nice few books (rules) but other than that I see no reason to join. I have not heard anything about the organization that really helps me at all (selfish, yes, realistic, yes). Other than getting the whopping 5$ off for being a ussailing member when signing up for regattas, it makes no real sense.
As Eddie murphy said
"what have you done for me lately?"

Maybe it would make a difference if I were a top 1% sailor, but I ain't.
I guess I don't get much from belonging to my professional organization either and that is markedly more expensive though.