If you tell a child, "Take care of this rule because if you don't you will be punished," the child has two doubts in his mind: Maybe I won't get caught, and if I am caught, maybe the bad thing about the punishment doesn't outweigh the good thing about the crime.
The child must know that there is an eye watching, an ear listening, and an unseen Higher Power to whom he is accountable. This awareness is essential for a sustainable civil society.