While substances can efficiently help someone destroy their life, keeping them away from drugs won’t stop them from destroying their lives. There’s something already broken in these people that they need to fix before it’s too late.
There are perfectly legal alternatives that can be just as effective with a little more effort. Putting heroin in your arm is just quicker than downing a fifth of vodka, or chasing dopamine at the dog track.
Furthermore, heroin != vodka in terms of how addictive it is for the average user, and that's partly why only one of them is legal for recreational use.
Controversies about decriminalization aside, harm reduction exists as a studied component in addiction, public health, and psychology circles for a reason.