In a logical world, where things make sense and people make decisions based on information and reason, a program that failed, especially so miserably, would be immediately ended and a new and better approach sought by analyzing what went wrong.
We don't live in that world.
Instead, we live in a world where it is politically better to support a failed counter-drug program than to admit that a counter-drug program failed. No one wants to be seen as soft on drug use. Last year, I took an evaluation class that looked at a similar problem with the "Just Say No" campaign, which had the perverted effect of actually increasing drinking and drug use among participating students by a significant amount, but no one would vote to eliminate funding for it because no one wanted to be the one who didn't support counter-drug measures targeting our youth.
I stand by my assertion that the best way to manage the international drug problem is for the US to legalize drug use. Prohibition allows only one enforcement response: jail time. In these days when we know that our fancy programs and the threat of jail are not working, and jails are increasingly bursting at the seams, it makes infinitely more sense to legalize and regulate. I'm not the only nutcase who thinks so: Milton Friedman wrote a paper on legalization. Below, a quote from the linked article:
"So what's the alternative to this failed war on marijuana? Contrary to claims by Drug Czar John Walters, the alternative isn't "surrender," it’s common-sense regulation: Take marijuana out of the criminal underground and establish sensible controls. Treat it like we do alcoholic beverages, with everyone involved licensed and required to follow a strict set of rules. Educate teens about the dangers of drugs with materials that treat them with respect and present the facts honestly."