Most poor city kids are born to parents who are not married. Half of those parents say they will marry. But only 15% actually do. For the rest, most lose contact with their fathers. If mom has kids with a different man, dad is likely to be gone for good.
I think this is the bedrock of why poor neighborhoods are a tangle of pathologies. As Kay Hymowitz says, the instability of their homes is more damaging to poor children than the poverty.