It's about solidarity. You see an oppressed group and you make yourself a part of their struggle for liberation. You aren't going to face the oppression they're fighting against yourself, but you identify with them anyway. At that point, once you're a part of the movements and are struggling along side S/GM's, I think it's logical that acronyms describing the movement would acknowledge that you're there. Yeah, some people want applause, but there're other reasons to want an extra a included.