Quote from nutmeg:
If someone calls and says that they hear a woman screaming "help me" like bloody murder in my house I at least want the cops to come to my house to check it out.
--------------------------
Bingo. What is missing in the equation regarding kids? They can't scream "help me, help me!" Hence the mandated reporters, anonymous hot lines, Cps showing up at the door.
If CPS knocks on your door and you refuse or are unable to answer their questions you won't leave them much choice except to remove the kids.