Because now it is recognized that you beat your wife at your own peril. Although we still have got the notions of reasonable chastisement borrowed from the British behaviour code. There is no permission to use the rod on the wife. Her redress is through divorce. Not everybody wants to divorce.
Many women think that a battering husband is better than no husband at all.
The parental responsibilities of a child are not statutory. We say that parents have the obligation to bring up their children in a proper way, and we leave it there. I think that would not be progressive legislation. I think you can eradicate that more by social education and awareness creation, than by legislation. When I was younger sometimes I preferred to get beaten because the matter is settled, is finished.