Austin Morrow
Headphoneus Supremus
I loved SkullCandy until I visited Head Fi, if course.
I haven't been a teenager in a couple of decades, but I have to admit I actually like the looks of SOME of their stuff.
As for why teens would like them, well:
Some aren't exposed to better, but they also might not know the difference.
They have massive market penetration. You can find them everywhere, Best Buy, Staples, small record stores.
Which leads to Grouping Behavior. How can everyone else be wrong?
And finally, some folks don't listen to music for detail, they listen for how it makes them FEEL. Some folks actually care more about the lyrics or the image the entertainer portrays than how crisp the snare sounds...