Meeting Tug of War

I am talking about meetings with the client in particular, here. If you have eight people from your company and five from the client, that is actually a conference and no longer a meeting.

Why do most of us mostly have more people than needed for most  meetings? 

Is it because everyone is needed in that meeting to represent their unique specialities? 

Or is it because we cant find that one person who can integrate it all and present our company perspective? 

Or is it because we all feel we must contribute something to everything that passes us by and say 'amen!' to all that we encounter? 

Is it that we feel so insecure about our capabilities that we take courage from company and feel comfortable in a crowd? 

Or is it that we involve lots of people so no one is accountable and everyone can survive a failure?