Michael writes an essay on hobbies worth reading in full that touches on his father, work, and hobbies. He writes about his father finding flying small planes enjoyable, only too late to fully enjoy it at the level he wanted to. (Failing health prevented his ability to see, and therefore fly.) Michael also writes about finding happiness in a job, rather than a career, so that he could find time for hobbies that made him happy.
My definition of "hobby" would include mentions of their productive—or redistributive—natures, rather than consumptive and are activities we would happily postpone or cancel other activities for. The best example for me is that I read to pass the time, usually while waiting something, but I often can't wait to write, especially these days. The word "hobby" implies to me an activity for which a person is not paid, but which they would not merely be happy do for free, but if they were paid for it, would resent making what they enjoyed previously feel like work. (Not getting paid does not imply a lack of professional quality in the output of a hobby, though many amateurs strive to create things with professional quality.)
See also: "Quitting the Paint Factory, an essay in praise of idleness.