I understand your point, although I would say that the speed limit is rather more directly related to harm to others. My view is that young people will refuse

I understand your point, although I would say that the speed limit is rather more directly related to harm to others. My view is that young people will refuse to be lectured on the dangers of drugs by politicians who themselves enjoyed drugs during their youth. Unless that politician's got some kind of personal horror story, such as "heroin killed my entire family", then their opinion will not carry much weight. Kids look at them, see a bunch of basically privileged people that had a wild time and enjoyed all sorts of illegal drugs at college, and then packed it all in when they finally got a good job. This is not a great platform to preach from. Young people ask, "if they can do it, why can't I?"