Professional vs 2nd Income

Based on a few months of browsing through posts on this and other forums, it seems that most poker professionals don't really enjoy the game anymore.

Given that anyone with the talent to go pro could also make a very nice side living while still holding down a job w/benefits, why do people choose to do this? Hate working for a boss? Like to set your own hours? Higher aspirations? Love the money too much to let go?

People who play professionally often complain on these forums of boredom, burnout, and unhealthy emotional swings. Wouldn't part-time play with a full-time or part-time job be healthier and add to your enjoyment of the game?