I wish to expound further: The criminalization of possession and cultivation/fabrication of certain substances has created a highly lucrative black market providing revenue for entities that are less that concerned with our social welfare and more concerned with maintaining a hegemony of power.

Just a clue as to the overall impact lies in noting that the USA is the single largest consumer of Latin American cocaine production, and the role this has played in creating a climate where cartels drive governments. (not to mention black money opportunities for shady governmental entities to dip in and out of, a la Oliver North...)