About 35 years ago, a friend of mine was getting married and simply could not afford a pro. It was either me, or other guests pooling what they took with their Instamatics. I studied our own wedding pictures, did the shoot, (which completely killed any fun I was ever going to have), and they turned out really good. I've been asked ten times since, and have said "not a chance".
I'm with Benjiboy, I don't need the stress and I don't need the money.
I think today, you'd end up with a lot of pictures of the backs of peoples' hands, holding up their I-Phones right in front of you, to make sure they got that important picture they wanted. Their rudeness at times is startling.