Because it is unnecessary.
Those are not commandments and, thus, are not obligatory. While sometimes useful, the Proverbs are basically King Solomon's fortune cookies.
Christian parenting
Leo Taylor
Jayden Gomez
Reminder that physically abusing your children is sinful and that the image of you using your power to hit your defenceless child will be ingrained in his mind forever which will cause him to love you less than he would've if it weren't and it will remain a traumatic dark experience of his life whether in the future he pretends that "it isn't a big deal" or not.
May God have mercy on your soul if you're the abuser and believe "it isn't a big deal".
Isaac James
He that spareth the rod hateth his son. Proverbs 13:24
Brandon Wilson
See:
Cooper Reed
Bump