Parents have been running their kids off since there have been parents and kids, because they're poor, because they don't like the kids, because they didn't want any to begin with, because they're bored with them, because they're sick of the concept of kids" My friend is more cynical than I.
Your friend is right. Sadly. I worked with children from "troubled families". Abandoned children, abused children, children who were uncared-for, children who were beaten up by their parents, children who rarely ever got a warm meal at home, children who were allowed to play with their Christmas "presents" for only one day, then the father sent them back to get his money back. And on and on...
And I had only the "less bad" cases. Because all the children still lived in their families (or lived again in their families after the parents decided to give it another shot) and were not given to the youth welfare office. The really, really bad and worst cases are the ones you see when working at the youth welfare office or a children's home.
A schoolmate of mine came home from a trip with the school and found all his personal possessions outside the flat in some bags and suitcases. Literally. His single-mother had decided to move in with her boyfriend during my schoolfriend's vacation. He was 16 then.
The boyfriend of my cousin had to move out when he was 18, too. Same story: his single-mother rent a new flat together with her boyfriend and cancelled the old flat. No more room for him. The parents of his girlfriend (my aunt and uncle) took him in. They also took in a (female) friend of their other daughter for some months, who was Turkish and had bad trouble with their strict Muslim parents.
Such things happen far more often than you may think. So sad.