From a simplest view, one of the reasons why so many crimes are committed is because there are so many laws, many of which should be removed from the statue book.
Apart from the medical side, many of the problems associated with drugs are because they are illegal, just like prostitution and formerly the porn industry.
If people want to kill themselves with drugs, alcohol, smoking etc then as I see it, it is their problem. Why should my taxes be spent trying to stop them?