The infrastructure hasn't changed at all (ie. stores and work places are still far away from most places where people live) and so having a car or a similar degree of range in transportation is a necessity and not a option. Its a matter of economics.
Well to completely disagree with you the infrastructure has completely changed. Stores are dying... Amazon is ruling. Kids as always tend to work part time jobs that are well within the range of public transport (which has gotten much better, and in many larger cities makes more sense even for us old folk). When they get a bit older and into the real work force more and more people are working from home. If you work from home, buy 90% of your goods online, and have a grocery store a few blocks away. Why the fuck would you waste money on a car ?
I also disagree that its a matter of economics. I am in my 40s... did I get a brand new car when I was 16 ? Fuck no. Used jalopy sure. New cars aren't really any more expensive now then they where when I was a kid. Even if a kid was going to buy a new car or have one bought for them... its all well and good that 33k is the average price, but young kids getting new cars get economical hatchbacks as they always have.
On top of all that the internet is raising a lot of young environmentalists.
I have 4 kids with a pretty good range in age. My oldest boy wanted a car when he hit 16 and got himself a beater to work on. The second one did the same. The third boy is 23 now and doesn't drive, and has no intention of ever driving. He takes the Bus to work, they order plenty of stuff online... they walk a couple blocks down for groceries and take a cab back if they get more then they want to carry. He has absolutely no need for a car really. My youngest, my daughter is 14 and I also doubt she ever bothers driving. Off topic a bit...she is going to cost me a fortune in schooling for sure, this summer she has spent 3 weeks at the University doing summer medical courses. Her I want to be a doctor was cute at 10 I figured she would move on, my last hope was blood and stuff would gross her out. Instead she now loves showing people pics on her Iphone of the heart she helped dissect. Things are starting to ache already, my bank account is going to take a pounding... my point being I doubt she bothers with a car for a long time either.