Most of my career, I had a front row seat to what substance abuse can do to people. Its not pretty. A lot of folks have dependent personalities, and its not always as easy as saying "Im just gunna quit". And not everyone is your classic, steryo typed drug user. How many posters in this forum need a drink, or 3 to "relax" after work? How many take pain pills for that "sore back", you know, even when it doesn't really hurt that bad?
A good friend of mine has a 25 year old son who lives at home, has been in and out of state prison for heroin possession. Really a nice guy, smart, and would just about give you the shirt off his back, but just cannot kick the habit. Last summer, his mother found him the bathroom with a needle in his arm, not breathing. Luckily, she is a nurse, and gave him mouth to mouth until the paramedics could arrive and inject him with Narcan. He still cant stop.
And TommyT is right, street level smack comes mixed with all sorts of strange stuff, and sometimes its so potent that a batch will kill dozens or more in a day. That's happening right now in Harrisburg, PA - over 20 dead. Mostly college kids and decent working people with a problem they cant kick. Its easy to just say screw em, they deserve what they get, but if it was your 17 year old daughter, or some other loved one, would you feel the same way? Not trying to preach, but a lot of people just don't understand how complicated addictions are.
Larry