The KEY for CASA is the person is on the infant/child/teenager's side, and only on their side. They have a "cleaner" influence than the social worker, "parent(s)", and even cleaner than any foster parent. There is no "book" for getting the best result for the child, so their CASA worker is the one to speak for them and make sure they get all their needs met using whatever resources are available. Interestingly, none of our fosters had a CASA worker that I can recall. Lack of volunteers was the issue. In the case of our first adopted, we petitioned the court to be declared de-facto parents, and became precedent setting our naive selves. Somehow, the universe paired us up with an attorney who was looking for such a case!
One minute in the foster system can (state dependent) open up a lifetime of access to benefits for the child. The child needs to learn these things too, as it may be up to only them some day.
While we are no longer active foster parents (we do emergency respite only), we do participate by helping foster families, adoptive families, and families with special needs children/adult children navigate the "system".