Haha, I feel like echoing my earlier statement:
For many it's a size thing. Some say it looks bigger for both that person and for the others that see it. I've never really cared enough to pay attention that closely, really. I've tried it once out of curiosity, and it wasn't for me. I've thought about trimming, but I never really cared enough to go through with it.
Gay guys can be picky about it though, I've noticed. I've been asked by guys why I don't shave or trim, and as mentioned in the other thread, I know some even get stimulation from the idea of shaving their partner's pubes (which is a bit weird to me, but to each their own I guess).