Yes
Yep. I'm a cop and I regularly deal with people that have been given free drugs to get them hooked / keep them in the circle in which they find themselves.
Although, to be fair, the majority of these people are either rehabilitated drug addicts (other druggies don't like to see people get out the gutter, so they'll give them free stuff to bring them back down) or girls going into the sex trade as a way to keep them in check.
So, yes, it does happen, a lot sadly.