It seems you tried to stereotype the distinction between longboarders and shortboarders. Although it is true that once you hit a certain age you're not going to pick up a shortboard and hit the halfpipe, but most young skaters are just not exposed to longboarding. When they are they seem to like it a lot. You failed to note that a very small percentage of kids even stick with skating and are able to pull off the tricks. Most shortboards are left in the closet after a month. As longboards gain popularity you will see younger kids riding them.