Having worked with many, I have to believe it's more a mix of things. There were certainly cases of hard luck, but it's also not hard to see that spending your paycheck on beer every week when you have no money is never going to improve things. In reality, it's more a mix of things, some bad luck and some bad choices.

Now it's true that some people can absorb a whole lot more bad luck than others because of their family, but I remember one guy in particular who was rather determined to send his life into a ditch in spite of having parents who were willing and able to do a lot of things to help him. He managed to do things like going to prison for beating his girlfriend and robbing her sister and endangering (and injuring) himself on the job.

So it's not all black & white like you're making it out to be.

EDIT: I do feel I should put in a counter-point, in that I also knew a guy who made about one bad choice and the rest was hard luck, so there's that too. Most people were more a mix and for whatever it's worth, I tried to help where I could. The guy who loved to drink had his cruddy old bike stolen one Christmas, so I gave him a brand new one. That was pretty important to him, as it was how he got to work. I put a headlight on it too, as he had to ride a lot at night.