Why do you think grown-ups say the kind of things mentioned in the poem? Is it important that they teach children good manners, and how to behave in public?

The grown-ups say such kind of things in order to teach their children good manners and etiquettes. Children learn how to conduct themselves from the instructions and examples of their elders. It is important to teach the children right conduct so that they behave like a responsible citizen when they grow up.