The best reason to join is to support the breed you like. And more importantly support the hobby. The few members I met in person and compete against are very nice and knowledgeable. They want to help you get what you need to enjoy the breed. And as OSUMAN will testify they will help you get some nice Buff Bantams. That is the best reason i can think of why to join.
It is what you want it to be. I joined after I talked to several members. Julie was the first member I ever talked to. It is her fault I am so addicted. She refered me to Mrs Pontious and then I was sent further out till I found someone who had Blacks. At the time I had my Milkey hens. When I got my Black birds shipped to me for just cost of shipping, they were immediately slaughtered that same nite by a pair of Racoons. I lost 3 of my 4 milkey hens, the new to me Black cockerel and one stellar black pullet that was part of the trio I recieved. only to feel like cr@p, and have the same breeder send me another trio for cost of shipping to reset my needs. Now that is what I call a great member of the UOC. And I feel blessed that I joined. I am hooked and Orps will be here till I croak.
I am also a member, which reminds me, it is almost time to renew my dues. It's very reassuring to know that the officers and "most" members of the UOC embrace every type of Orpington, English and American, and every member, whether they show or not.