Men are from mars.....but mars is more sensitive than it makes out to be

So I was doing some realizing today, and I began to wonder about something. I've noticed that whenever one of my guy friends get's a girlfriend, his other friends start complaining about how they never see him, how he spends all his time with her, and how they act differently around the girl. But on the female side, whenever a girl I know get's a boyfriend, all I notice is that her friends, for the most part, are just happy for her. They may get a little of the "always a bridesmaid never a bride" syndrome, but for the most part I don't see them complaining. And I could be wrong about that, since I'm not a girl obviously, but what's the deal with that? Why are guys so pissy when one of their friends starts hanging out with their girlfriend? I'm not saying I'm exempt either. Almost all of my close friends have girlfriends right now, and to be honest it's kinda weird knowing that if I really want to hang out with them, I either need to invite their girlfriend, or they're pretty much not coming. I know I've ditched my guy friends on a few occasions to hang out with girfriends I've had, but it doesn't keep me from complaining about it when it comes back at me. It's also interesting how most of the time guys say that their friend acts differently around their girlfriend. Now I can't speak for all men, but I know for a fact that if most of my friends acted the same way around their girlfriends as they did around me, they wouldn't have a girlfriend. Do women get like this when their friends start dating? It doesn't seem like it to me. Just some food for thought.