The problem is that the law doesn't differentiate between those who use occasionally and those who abuse (and leaves aside the whole question of whether drug abuse by itself is a public health issue or a law enforcement issue).
The laws regarding alcohol do make such a differentiation. If you are drunk in public (or even just possessing alcohol in public), most locales can arrest you. If you drive while impaired, if you furnish it to minors, both things that are arrestable.
But the notion that teh state should be passing legislation, or not, based on making us all the best we can be is creepy at its core, especially considering who's in power currently.
Just curious, would you be okay with legalizing other drugs?