Since you're all too lazy I'm taking this into my own hands.
Courtesy of 1337 aka Young Jameson.
As you can see, we have a good amount of x-games athletes and other professional riders on this list. Consider the fact that they enjoy the event as a whole, and aren't simply competing to milk the system. Furthermore, the athletes worked hard for the skills they have regardless of their past accomplishments, just because they won X-Games it doesn't mean they get handed a medal. Without riders of this caliber competing against ams there'd be no motiviation for those young ams to work harder.