Bog knows, the amount of time and law enforcement resources spent on enforcing "vice" laws is enormous. But after all, we disposed of Prohibition after damage had been done in creating organized crime despite the fact that rigorously-enforced Prohibiition laws could criminalize a large portion of the population. Whereas we have not nationally repealed laws against marijuana and other non-harmful drugs despite similar damage. And it's not like the ruling class was inconvenienced by Prohibition and therefore protested enough to force repeal.
However, the difference could be that in the period of Prohibition after the Depression, we had less surplus labor to warehouse in prisons than we did when marijuana became a scheduled drug. Obviously the later '30s are a different period from the early '70s. Even if this were the case, though, I still find it curious that true capitalists have been willing to forego the profits which would accrue to legalization for so long. But then, we've had prostitution laws much longer, and there's surely a lot of money to be made there.
-- Mal