Why do parents tell this to their children?

During my police career, there was one statement that parents would make to their children, that really ticked me off. “If you are not good, that policeman will take you to jail”. I have told many parents not to make this statement to their children. Being at an impressionable age, children grow up to believe the police are something to be afraid of and never approach them, if help is needed. Question: What’s your opinion of this statement? Did you or have you ever made this statement to your child?