Yes, they often do. And the reason for that is drugs are expensive. And they are expensive because the dealer takes a risk to run his business.
I'm not suggesting legalizing all drugs. Cole, crack, PCP, and bath salts for instance, cause people to do some really violent shit. MDMA or weed on the other hand just make people happy, sleepy and hungry. So legalize the drugs that don't hurt anyone, tax them, and put that money into rehab for the hard drug users. It works very well in Europe.
Turns out if you give heroin addicts methadone every day they don't bother anyone by panhandling, leaving dirty needles around, using public space as their own personal restrooms, etc.
As you might have surmised I have a very broad libertarian streak where drugs are concerned.