Would you expect something else? I'm not seeing anything funny about it. The vast majority of harm comes from the illegality, not from the drugs themselves. Do you want to reduce harm, or do you want to impose your morality on other people?
Well since you asked, no, I would not expect something else. Their (your) addiction has affected the organ that they use for making decisions. I would expect an addict to find any way he or she can to find access to more of the addictive substance their now compromised brain demands. Being smart or high functioning only means they can find even more clever and inventive ways of achieving their desires.
You say that the vast majority of harm comes from the illegality of drug use. I don't see any reason to believe that is true. You haven't presented an argument or evidence to persuade me one way or the other. On the contrary, I think addiction is itself harm. It removes the ability to choose.
It attacks the very organ that makes your choices.
You have access to resource, so you can mitigate the consequences of your actions more than others. Remove your resource, or replace it with a $40,000/year salary and a tough service industry job, and the consequences will find you. I think eventually the consequences will find even you, however much resource you have amassed. You should make a pact with yourself to see if in 20 years (assuming you make it that long) you still think your life is as good as it could have been without your addiction.
Do I want to reduce harm or impose my morality on other people?
My answer is YES.
I want to reduce harm by imposing my morality on other people. Any time you vote you are imposing your views on ethical issues onto society. Let's all agree that everyone imposes their own views on morality onto others. You are doing it to me right now, and for that I thank you. Let's duke it out in the public square. If you convince more people with your arguments, your views will be codified into law. If I convince more people with my arguments, then my views will be codified into law. This form of reasonable discourse is how we avoid solving our issues with violence.
Look up the studies for areas where it is decriminalized and areas where certain drugs are legal. Portugal would be a good place to start. Let Google be your guide.
I understand what you're doing, shifting the work to me, but it is generally courteous in a discussion to provide an argument to support your points. Why should I do the work for you and then let you sit back and pick at my arguments? I am not making a positive statement either way on the issue. You are the one that has made the assertion that illegality of heroin is the primary causal factor in it's being harmful, so you are the one that has the onus to provide supporting evidence for your claims.
I'm being downvoted because I started this off being snarky and, frankly, an ass to you. I think my points are still valid but it's not a kind way of communicating them, and for that I apologize.