There are currently 1.3 million adults in prison(
source ). Of that 1.3 million, 24.7% are incarcerated for drug offenses (
source ).
In 2002, there were 840,000 police and detectives in the United States (
source). In addition, there are 695,000 lawyers (
source), 200,000 paralegals (
source) ad 84,000 probation and corrections officers (
source) working in the United States. That is nearly 2,000,000 people in the United States working in an industry which relies on crime to happen.
If we were ever to "win" the War on Drugs, 25% of these people, almost 500,000, would be out of a job. If that were the case, politicians who really fought to end the drug problem in the United States would lose the support of police groups across the country and would themselves be out of a job. That seems to me like a pretty good incentive to perpetuate the drug problem in America, rather than end it.
Just a little food for thought.