How should a doctor know how to treat you if you don't tell them what caused the problems? Doctors don't just hear you list a bunch of things you are "feeling" as symptoms and then output a pill to take. They need to look at your overall health, wellbeing, symptoms, medicine you are taking, diet, etc.

You can't just show up to a hospital with crack or heroin withdrawl and be like "I don't feel well, please help me". They are going to ask why you don't feel well.

I'm talking just human nature here. If something is forbidden , illegal, subjectively immoral, etc. then it's difficult to both admit and seek help with that thing. I don't have any data to hand to back my assertion that criminalization negatively affects treatment, however if such data exists, then it would be less surprising (to me) than the inverse (criminalization makes it easier to get treatment).