All of your arguments about "safety" fall short for that simple reason.
Well, I don't have the statistics handy, FreeTally. (I just saw this thread this morning!) - I know two people were crushed by a car in my town last year driven by two kids high on cocaine. One died instantly. The other died from massive and painful injuries and loss of blood - within an hour of the accident. He pleaded with those at the site to help his wife and children (and the town and churches have done so) - since he knew he was a goner. One of the kids escaped relatively uninjured. The other lost a leg. If requiring kids to be drug free when they get licenses would save at least two more such people (which of course it will), then I'm for it already. Further, one of my family (or friends) could easily have been that guy who was crushed and bled to death that night.