Good point. Money is necessary for living (food and shelter is almost never free), but if you are lucky, you can choose how to make them. Some people thrive while earning money via their hobbies, other fair better doing it for themselves only. It doesn't mean that you cannot make money doing what you love, but there still needs to be something to do just for the joy of it. Because, once you get paid for your hobby, it becomes work. And with work comes the feeling of constrain and deadlines, and the pressure to produce results that are worth money you're getting paid.