That's a really good point you make. With alcohol, there are some very good real-world warnings to youngsters about its dangers. One thing that comes to mind is here in Jersey around high school graduation time, nearly all of the county sheriff's agencies provide a wrecked vehicle in which people died in to display on the front lawns of the schools. Simple, blunt, and effective.
Contrast that with some of the idiotic, hysterical, poorly acted, and inaccurate propaganda that the federal ONDCP puts out with regards to marijuana. It's no wonder why teens shrug them off and have no reservations about using pot irresponsibly.