Alcohol is a bad example to compare vices too. It is definitely a very dangerous substance, nobody argues that, but it is so ingrained in many countries cultures that outlawing it would be political suicide. In fact, it was already attempted in America, we saw how that went.
Prohibition didn't fail because alcohol is actually a 'safe' substance, it failed because it is addictive and people wanted it back. Allowing other substances to gain this status should be done with _extreme_ consideration.
Disclaimer: I think psychedelic's do have valid medicinal uses, but I have also had a very bad mushroom trip before, I know what they can do to your brain. My personality was forever changed.