Because he's going to drive like a dumbass until he does. I think you would prefer that his first 1-2 accidents are NOT in a TTZ. It always takes teenagers a wreck or two before they wake up and stop driving like dumbasses, regardless of anything else that ever happens.
They will be much better drivers in the long run because of it. It's the ones that just barely skate by and never have an accident in their teen years that end up driving like dumbasses for the rest of their lives.