No, I don't think it is strange. It has little if anything to do with "poor and minorities" or "inner city". It is about purpose for use and the credentials of the supplier.
People trust doctors. People expect that this will not be a problem. People have sympathy for those who are addicted due to having, perhaps wrongly, trusted a doctor. That doctor is a paid professional, highly trained, and expected to provide for your health.
Consider a similar situation. A person gets a house built, moves into it, and it collapses. They might have hired a licensed general contractor, or they might have paid a random person they found sitting outside the hardware store. The difference matters. Similarly, one could hire a licensed pilot or somebody who took just a couple lessons. You may die either way, but one way gets much more sympathy.
There is also the matter of need. The doctor is supposedly supplying drugs for a purpose beyond "it would be fun". There is no respect for people who gamble with their health just to have fun. Somebody who just got a hip replacement is understood to need painkillers. Visible needs are obviously legitimate. If there is no visible problem, the assumption is that the usage is just for fun.
BTW, for these purposes, the start of the addiction is what counts. The current drug supplier matters much less than the initial drug supplier.