As I study more of these pictures (and by study I mean look at a couple of them for a couple of seconds), I think I begin to understand them more. You know how people have photo booths at their events nowadays? Those photo booths always have a bunch of props like large sunglasses, silly hats, and swords. There must be a table of props just out of frame of all these photos. That would account for all the umbrellas. I can't help but doubt that many people were constantly around umbrellas.
It is important to note that taking photos was a much more sacred activity in the past. Now I just bust out my phone and talk pictures of girls as they walk by. My girlfriend keeps telling me I need to stop doing that.