I profoundly disagree with your definition of hobby. My "hobby" is writing a science fiction novel. I don't get nearly as much time to do it as what I do for my day job, but I try hard to approach it with the same degree of seriousness that I bring to my work. So far, I don't think I've written anything anyone else would want to read, but I've managed to get to the point where I actually enjoy the process of writing.
Even better, I can sit back after I've written a chapter and say, "yeah, that actually embodies what I wanted to say". There is a very profound satisfaction in being able to do that.
I agree that many things we do in our free time might not have the qualities I describe above. I do such things too. But I would suggest that hobbies can be serious endeavors, and that the very fact that we love to do them makes them powerful.