This blanket statement heavily depends on which specific drug we are talking about.
Or rather, do you feel the same way about alcohol and nicotine?
It is not clear to me if law in fact incentivizes good behavior. In general my view on these matters -- social architecture -- is that form can not engender meaning. Meaning needs to be project into form, in the sense of it being an expression of collective understanding. This brings up the matter of pedagogical aspect of social order, to wit, your views would be entirely orthodox in a strict patriarchal societal order. And our society is no longer that, as you must know.
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"The most important things about beliefs are whether they are true. The most important thing about motives is whether they are good."
I saw this on your profile page. What is necessary is that actions are timely and true. As to "good", I hope we agree that what is true is by definition good (if timely) and what is good can not possibly be false or untimely. So in my opinion, it suffices to say "Be timely, be true".
For whatever reason the west fails to successfully socialize an unacceptably large portion of the native born population.
And yes, immigrants generally tend to end up lower on the social hierarchy in their new society as compared to the old one, but how is that relevant to what I wrote?
Part of the reason for that is protection and promotion of freedoms of individuals, which means that we expect the society to stay away from our lives, because we did try various forms of state and church hierarchies running our lives and we did not like it. If you come to the West or are born here learn what it is about and decide how you want to live your life. The same people complaining about the society not caring for all are those who wanted the society to leave them alone.
In the first case, one end of the law is to teach good behavior by punishing what is bad, and perhaps incentivizing what is good. Drugs are opposed to the objective human good, and gravely so, for one, because they cripple the effective exercise of reason. Any attack on reason of this kind is gravely immoral, and constitutes a direct assault on human flourishing and what is most essential to human beings. The result is the degradation of the human person and the degeneration of society. The common good suffers greatly, as you have described, and since the primary purpose of law and the governments that make law is to guard the common good, it falls to governments to criminalize and regulate drug availability and use.
In the second case, ask yourself why anyone takes drugs. Unhealthy curiosity. Boredom. Escapism. Mental illness. There is no legitimate reason for drug liberalization as there is no legitimate reason to take hard narcotics recreationally (I emphasize that word because there is a place for regulated use in the context of medicine under the principle of double effect). Liberalization lowers the barrier of entry by signaling that using narcotics is no big deal. And yet it is a big deal. The instructive dimension of the law, by penalizing use, helps counteract the foolishness and frailty of human beings that would bring ruin to such people and those around them. Libertarian anthropology does not stand a chance in the face of reality.
(Obviously, plenty of substances are psychoactive, and I do not propose a categorical ban on everything from cough medicine to cigars to Merlot to coffee. I am no teetotaler. We know what kind of drug use is problematic when we say “doing drugs”. Prudent regulation that takes into account a number of factors like the severity and nature of chronic and acute harm, how addictive something is and its potential for abuse, dosage, etc. It’s one thing to chew on a coca leaf, another to snort 30 mg of powder.)