Well, why would they crack down on heroin? We can ask the same question. Is it their concern what i do with my body? No. In fact, if i want to kill myself and you physicly prevent me from doing so, you are guilty of false imprisonment (assuming im not putting others in danger by jumping in front of cars or of a building, of course), why then should i be prohibited from at worst slowly killing myself? Which isnt even neccessarily a given, there are people who smoke some heroin every other year. In fact it has no lasting consequences aside from possible addiction which is at least as much psychology as it is biochemistry. And, yes, you can OD, but thats only really a problem due to it being illegal and people therfor receiving inconsistent quality.
Now, if you were to say you dont want to pay for any recovery, youd have a point - for it being taxed to the extend as it causes costs.