I'll go out on a limb and say that while I enjoy photographing alone, I have a lot of fun when I'm with the right group of people and it becomes a lot more fun.
It's interesting to see how people see the same item differently, and a lot of the fun is seeing and comparing everyone's shots afterward. I think a lot of it has to do with the group of people because people are happy to kind of do a little wander to the side and come back to the group. Then again, our group is also just as happy meeting up for the social side of things and meeting for pizza or something.
I think it fosters a bit of creativity too since you get to see people taking shots that you may not have thought of. Plus you get to engage in meta-photography
Who else but another group of photographers is going to understand why someone is laying on the ground taking a shot lol