Those who are convinced by the argument for prohibition of substances are encouraged by politicians to conflate it with fighting drug use. When the 18th Amendment was passed in the United States, prohibiting alcohol nationwide, there was seen an initial decrease in alcohol consumption of some thirty percent but this was soon followed by a dramatic increase by as much as sixty percent as compared to pre-prohibition levels.
Not only this but the prohibition encouraged the development of massive black market infrastructures which fed alcohol profits directly into the pockets of criminal organizations instead of peaceful businesses. It is fairly simple to extrapolate from this the source of the current drug proliferation when comparing pre-prohibition levels of drug consumption with that of today. The drug trade has not suffered but, in fact, thrived under prohibition. It inflates the price of the substance, increases profits, encourages purposeful "drug pushing," and empowers criminal enterprises, making us all that much less safe. The good intent here of people who are for prohibition is in decreasing drug use and addiction.
People do not quit drugs because they are prohibitively expensive, they instead turn to a life of crime or play on the emotions of those closest to them. People quit drugs when they wish to and they only do this when they have a good reason. Often they can only do this with treatment and help, though by the time they are ready to stop, they have already expended the wealth of those most willing to help them due to the excessive cost of the drugs.
Believing that you can legislate away the evils of society is a utopian ideal, not libertarianism. Freedom scares most people.
But I understand where you're coming from now that I know you are from a LEO background.
The supreme art of war is to subdue the enemy without fighting.
~Sun Tzu