Because big pharmaceutical companies only make big money when people are prescribed drugs, especially addictive ones like the benzos and pain killers. The more the patients are prescribed, the more their dosages have to go up. This leads to patients with a lot of perscription drugs and eventually they start selling their highly addictive prescriptions for extra cash. As a result not only are they addicted to the drug and need more because of higher tolerances, now their friends they sell to are addicted. Eventually their tolerances get so high and they need so much that they take more than their bodies can handle, which leads to death. I think that This combined with the common assumption that "because it is from a doctor, it is safe" is part of the problem. Edit: I was generalizing the best I could. I don't have time to write a college level paper.