First you have to know that it's going on. And then someone has to report it. And then someone has to WANT to do something, law or no law.
And many, many people believe that it is a parental right to physically abuse a child (I'm not talking a simple whap on the bottom here, I'm talking beatings).

And they HAVE been prosecuted, unfortunately after the child is found dead or badly hurt. The defense by the parents that they were "driving the devil out" or something like that doesn't wash in the courts, either.

What was in the film is, in my opinion and based upon the description, greed and exploitation. Yes, it's wrong and yes, the child's life is probably twisted.