America's puritanical urges result in more self-harm than anything else. So much of the way our nation is structured is based on some ancient idea that you have to live clean and work hard in order to get to heaven. That is combined with a sense of justified sadism: if we catch someone not living up to these ideals, it is appropriate to punish them, and appropriate to take pleasure in punishing them.
The War on Drugs was never about public health. It was about 1. controlling minorities, and 2. moral superiority. So there's absolutely no surprise that a health-based approach is showing better results than a punishment-based approach.