CPS has rarely, if ever, concerned themselves with what is legal. In their defense learning your legal powers and obligations would be a lot of work. It is much more expedient to threaten violence against someone's children. It's very much like King Solomon only backwards. He threatened the child to figure out which woman actually cared about the child so he could return it to the parent. CPS threatens children and uses that threat to coerce compliance from parents afraid for their child's safety. Parents that don't care cannot be threatened in this way.
There are bad parents, there are even monsters masquerading as parents. No question about it, there is evil in the world. But in the final analysis nothing is more monstrous than a bureaucrat with super-police powers. An adult can rationalize: "Sure Mr Cop, you can arrest me on false grounds. I'll spend a day in jail and sue the city for $500,000". But when a sociopath is going to kidnap your child and put them into an unknown situation from which you may NEVER get them back - since there are NO objective laws in the first place, a parent simply can't risk it.
CPS are synonymous with home invaders. Maybe they broke into the home of a bad guy and the world will be better if they just shoot him. Maybe the people are completely innocent of ever even jaywalking. When guilt means whatever they want it to mean and you are guilty until proven innocent, perhaps 3 years from now, you just cannot take the risk.