Law enforcement was wasted trying to prevent the new crime which turned into an unenforcable battle with gang wars and corruption. Alcohol became all the more popular. These inefficiencies caused Prohibition to end after 15 years and alcohol was legalized. So how can the government admit that prohibition was a mistake, yet encourage a practically identical policy of drug prohibition. Especially since the most lethal drug has proved to be alcohol.
Fear seems to be the biggest factor against making drugs legal.
This logic is part of the problem. We can't look at the world as a group of idiots not to be trusted to take care of themselves. Our prison system will benefit as well due to a smaller population of inmates. Drugs are dangerous, whether they are legal or illegal. Drugs are available regardless of what our government does.