Group sex scenarios is that kind of thing which looks hot in porn to me, but then thinking about it, I really don't feel like I would actually want to partake in one. I'm assuming girls feel the same?
I wouldn't want to be one of the guys in a gangbang even if there's a nice girl there, and it feels like getting two girls to go down on you just isn't going to be actually worth the hassle to get there, nor the potential relationship risks.

I wouldn't actually want to share my girl with anyone else, so why would she want to share me with anyone else either?