There is an old pegasus tradition, passed from one generation to another. It roamed the winged horses' race for ages, having existed since the old days of Pegasopolis.

Or something like that. Truth is, Derpy can't quite remember it all. And there's one other pony not so sure about said tradition. Matter of fact, she never even encountered it before.

Then again, ignore popular trends all you want, they tend to catch up with you sooner or later.