A big piece of this is the neglecting of mental health. Many folks who cannot take care of their kids have undiagnosed mental health issues (often self-medicated by drug abuse, etc). Their kids end up in foster care AND may have those same, undiagnosed mental health issues. Depending on the diagnosis, behaviors can downward spiral into a criminal record.

This is not the case for everyone, of course. This is what I've observed teaching fostercare students, being a CASA, and being the parent of a kid adopted out of foster care. It's a challenging path for anyone involved.