I have a brother who's an addict. When I say addict I mean, he is an addict to anything addictive. Be it marijuana, gambling, alcohol, smoking cigarettes, whatever, if it is addictive he will engage it because he's a socialite, weak yes man. It just is who he is. He isn't a bad person, he's just a weak person (and by the fact that he has no trust by anyone due to his weakness for addictions, he'd almost admit this. He can't even get money loaned to him by his own friends).
Marijuana users are just genetically addict prone people. They aren't evil. They aren't even bad usually. They were just given a bad genetic chemical combo and were likely coded for addiction to various things from the second they were birthed. In that sense, I think it is more beneficial to regulate these people and tax them for the greater society rather than to believe you are ever going to legislate out genetically prone addicts. You aren't. Fact is some people got a good combo of industrious, responsible genes and some people didn't. Genetics is a very 'It is what it is' thing. Best to deal with that reality in our policy.