DCFS's goal is to keep children with family. The obstacle is timing: relatives must clear a background check before children can be placed with them, and that takes time.
Foster families are already approved and available, so DCFS may place children there in the first days of a case.
A relative can ask the court for placement while the case is pending. That request lands much better when an experienced abuse and neglect attorney presents it with the background check already underway.