Adding on to what levonda said. You can convince them that having a puppy will give you responsibilities because you are taking care of another living things. This can help prepare you for the real world. You will know how to take care of something or someone that is not yourself. You will have duties you must follow to keep the puppies needs. You will learn from consequences. For example, you do not walk the puppy. The puppy pees on the floor and in result you have to clean it up. You have now learned the important of walking the puppy and the consequence.
tell them that its teaches you responsibility