My Little Pony: Friendship is Magic - Yeah, why does Rainbow Dash want to become a wonderbolt again?

Well, they are glorified performers in the guise of some kind of Equestrian Air Force. When their greatest accomplishments have to do with selling tickets to their own aerial acrobatic shows.

Then again, that's also why Rainbow Dash wants to join them. Since all they do is perform and do tricks as fast as they can, which is stuff she likes to do. It's already established that she has an ego and enjoys attention for what she does.

They do seem somewhat overrated. We've only seen them in action twice (in "Sonic Rainboom" and "Secret of My Excess") and they failed miserably both times.