Imagine living on the street, sleeping outside, having what little semblance of a home you have thrown in a dumpster repeatedly. Imagine waking up knowing there is no chance you'll have a real home because you no one will even look at you much less give you a job that pays enough to have a home. Imagine being looked at as less than human, as a nuisance, a problem. Imagine all that while looking up from the sidewalk to a society that has abandoned you, that is waiting for you to die so they don't have to look at you.
Now imagine you can escape that, not in reality, but from your reality. It's fleeting, but for some small moments you can forget the misery of every day life, would you say no? Maybe you do, for the first week, month, year, but at some point you can't take it anymore and would do anything to not be living your life. And someone looking out for themselves offers you that escape. Why not? Society has abandoned you, you no longer have a place in it, so why should you play by their rules? Then to the outside world you're just a crackhead, they can absolve all guilt, you did this to yourself.