Let's start with the assumption that drug trafficing is a big business. Somehow, end users manage to come up with a lot of money. Few of them do it by criminal means, or we'd see much higher rates of violent crime. Few do it by living through their savings fast and then dying off -- we'd see higher mortality rates and also that process can't be sustainable. So either drug users are being recruited at a brisk rate (which seems unlikely, as it would encompass mos tof the population quickly) or they are capable of living, working and earning enough to support stable habits. In short, the image of a meth-crazed junkie misrepresents the majority of drug users, same as the movie "Eternal Jew" misrepresented its subjects.
There is so much wrong here it is hard to know where to start.
Many users are themselves dealers, subsidizing their habit by doing this. Areas with high levels of e.g. crack cocaine usage not surpirsingly have high rates of crime. I doubt this is an accident.
Further, I asked a public defender I know how many of his cases had involvement with drugs and/or alcohol. The answer was like 90%, and those arent possession/dealing cases. Those are robbery assault cases. In the 1950s when my father moved to NYC he thought nothing of standing in Harlem at 1AM waiting for the bus. By 1980 driving through in the daytime was hazardous. So, how high does the crime rate have to be for you say that "we'd see much higher crime rates"?
It takes a long time to die from drug use and addicts can have 10-15 year histories. Many of them dry out for a time before going back to it as well. But some drug habits, like crack, have shorter "half lives" so the user suffers far more physical damage than someone addicted to, e.g. Oxycontin.
Some drug users do hold jobs and support themselves. Some people drive under the influence and never have an accident. But I wouldnt use that fact to argue that enforcement of DUI laws represents an unwarranted intrusion on right and that DUI ought to be made legal.