On #1, I'd guess one factor is that the car isn't as big a part of teenage social life as it used to be. In much of the U.S., cars were central to high-school social life, with who had cars counting for a considerable amount of social status, and a lot of hanging-out activities (malls, movie theaters, arcades, etc.) requiring cars to get to. It's possible that also had advantageous effects for being able to get to jobs, but teenagers weren't mainly getting their licenses for those reasons. My read is that hanging out at the mall doesn't have the same role in high-school social life of the 2010s as it did in the 1980s.