This is a result of U.S. law being based on compromise. The legislature, especially in places like Utah, has been reluctant to stand up against the old "spare the rod, spoil the child" mentality. Instead, we count on people knowing how to beat their kids discreetly.
If these poor children had been girls instead of boys, I wonder if the police would have been a little more sympathetic to the harm being done.
"As long as the child within is not allowed to become aware of what happened to him or her, a part of his or her emotional life will remain frozen . . . all appeals to love, solidarity, and compassion will be useless."
-- Alice Miller