A puppy should not brought into the home to teach children responsibility. House training and discipline training are adult jobs. Teach your child to be responsible by doing dishes or taking out the garbage, not by being put in charge of a helpless animal with basic survival needs. Animal shelters and pounds are full of puppies, young adult or adult dogs who were brought home for all the wrong reasons. The owners didn't know about dog responsibility or personal commitment.
Puppies loose their cuteness.
They grow up just like humans. But they need love and care their entire lives. The adoption fee or purchase price of a puppy is nothing compared to the life-long cost of regular veterinarian and emergency care over the course of the dog's life. There are also licensing fees, equipment and the replacement of personal items which are damaged or destroyed. They are an extra household task.