The foster care system is a bit of a hodge podge across the USA.  It has been designed to protect children and remove them from harm's way.  There is definitely a challenge surrounding how to identify which children really need that protection.  As a society, we don't want to be in the habit of removing kids from their mom's and dad's for no reason--having this happen is a traumatic experience on so many levels.  Children often blame themselves for the bio-parent's inadequacies. 

They don't understand "normal" thinking that:

When a child is taken into protective services and is placed into foster care the kid is often assigned a case-worker, therapist, and a lawyer. The lawyer is called a "Guardian Ad Litem" (GAL) and is assigned to look out for the best interests of the child. While this lawyer is the child's representation, he or she doesn't necessarily represent the child's wishes when the wishes fly against what is safe for the child.