Drug users tend to associate with other drug users, because non drug users do not understand drug use and have a preconceived idea that they are intrinsically bad. Therefore, drug users are always around other drug users, and likely always around drugs, and therefore tend to do them more. When breaking a habit, you must stop your enablers, but drug users eventually mostly have other drug users as friends, so it is very hard to break the habit of drug use even after it becomes a problem. That is because they are always around drugs and other users and it takes a large amount of will power to refuse taking drugs when one is around it all the time.
As a result, drug users form a subculture. The drug user ends up alienated from his or her non-drug using friends. However, the cause is not the drug or the drug problem, it is the illegal stance society takes on drugs. One is a criminal if they possess drugs, so they will not do this openly, yet they can do this somewhat openly among the drug-using subculture, and possessing drugs in that subculture makes you high status in that subculture. Drugs and especially good quality drugs are of a higher value in that subculture, than being rich.