The 26.2, 13.1, Ragnar, and other stickers are just those people saying "Look how great I am" and tooting their own horn. Mayor of Cougartown can bench 225 10X's, but I've seen no sticker gloating on his car.
Runners also devote large chunks of time to what they are doing. Who has the time to run for several hours in the day? Certainly not the hard working folks putting in 10-12 hour workdays. The more wealthy that's who. So we've got egocentric wealthy people who enjoy this activity the most. Not to mention the costs involved with running in many of these events. What a better way to exclude poor people from running then to charge people just to run? Just another way the snobby rich people try to distance themselves from poor ones.
It's kinda just a snobbish "me me me" activity if you ask me.