If I'm reading your question right, you are asking why Child Protective Services doesn't work with the parent instead of the child?
If that's correct, then the fact is, they do. I am a foster mother, hired to care for the child (which is where my HUBS come from). But while I am caring for the child, CPS is working with the parents to reunite the family. They get the parents started in parenting classes, alcohol and drug abuse classes, domestic violence classes, anything and everything that will help the parents learn to parent their child in a good way. They have time to get a job and an apartment, to leave the abusive boyfriend or whatever has caused them to have their child removed. The parents are given a year to make progress towards learning postive ways to parent. If they work with CPS and are willing to meet even the most minimum requirements - and extensions can be made in regards to the time limit if they are making progress - their child will be returned to them. CPS also looks into the family, trying to find a grandparent, aunt, uncle, or any relative who can take the child and keep them in the family. Unfortunately, dysfunctions usually run in the family, and sometimes relatives can't be found who are stable enough and even willing to take the child.
Does this answer your question?