Alcohol is one of those double edged swords.
It has been around for thousands, if not tens of thousands of years. Drugs like heroin, cocaine, etc. are inventions of the last 100 to 150 years. Heck, George Washington was the biggest whiskey producer in the United States for several years. It was legal long before prohibition and in every part of society. There was simply no way to remove it Drugs were not widely used until the 60s, the same time the outright bans were being put into place. Most were already illegal without a prescription, which was extremely difficult to be legally allowed to write. Even today, the vast majority of Americans do not use illegal drugs and would not even if they were legal.
One can drink a beer or shot and not drop dead, or even be impaired. Take one dose of cocaine, heroin, ecstasy, etc. and you're spaced out or worse.