If you're looking around, wondering where all these authoritarian adults come from, maybe this is a clue:
The growth of a child under the tutorship of the parents is time spent in God's moral workshop being fitted for heavenly citizenship. As the child develops, the parents should accurately recapitulate the moral government of our Holy God. The rod is the parents' main tangible aid to bring the child to understand the judgment of God--and eventually the grace of God.
To the small child, the father and mother are the guardians of all law, the protectors of truth and the dispensers of punishment and reward. The parents are a window through which the child gets his first impressions of the foundation principles of Divine government. If you make rules and do not respect them enough to enforce them, you will be making a statement about law in general. Your responses to transgressions are stage-playing the responses of God. By application of the rod they will understand their accountability to God. Unless all transgression, rebellion and meanness of spirit be treated as God treats sin, the child's world view will be false.
The military uses real bullets in training the men to avoid enemy fire. Replacing the rod with hollow threats would be to your children like replacing live bullets with firecrackers. It would get the men killed later on.
Therefore, the proper use of the rod is indispensable to a complete world view, for the rod completes the concept of law and accountability. If temporal authorities do not honor the law enough to enforce it with punishments, how could the child believe the great eternal authority will be any different? Michael and Debi Pearl, "To Train Up a Child".