People are free to choose whether or not to have children. Human beings are granted freedom of choice. The decision to have offspring is, like many others, only a matter of personal choice and there is no duty here that we can talk about. The only real responsibilities towards society that people have are those imposed on them by law. (Paying taxes or protecting a country being prime examples of these). Because society has not chosen to create a law forcing everybody to have children, we see that choosing not to bear offspring is accepted by society.