How does a society function if everyone has the child's attitude? Who will grow the crops? Who will make the clothes? Who will build the houses? Who will keep the internet working? Where will all the consumer goods come from?
One component of a happy life: Find joy rather than drudgery in doing the things that need to be done. That is what Grandpa is trying to teach. He offers it with love. He wants you grow up to live in a happy functioning society, not a distopia where problems fester because no one will do any slave-work.