Process is much easier to change then changing people. Its why the government deducts taxes from you, instead of you paying at the end of the year (both because you'd spend it all, and you'd be pissed doing a bulk sum payment).
Likewise we have levers, should we be selling soda / pop with outrageous amounts of sugar in them without some sort of healthcare tax? I don't mind sugar being available, but right now its subsidized by our health care fees. My insurance is more expensive because of diabetes, heart disease, etc.
Marijuanna and sugar and a million other potential vices like alcohol and video games should be available.
But we should teach kids discipline, critical thinking, and impulse control - rather than playing whack-a-mole with every vice that comes along.