"Spending that many hours in casinos is not something I would want to do. The travel, the boredom, the time it would take to find and exploit good games, putting up with the general flow of jerks on both sides of the tables, the games one must play to avoid backoffs are not the stuff of any dreams I have ever had."
A pro gambler can spend very few, even zero hours average hours per week in a casino. A pro need not travel and can play such that he gets backed off much less than recreational players or even never.
Not many can achieve the above, but those who so chose and have the necessary skills can.
For me, the lifestyle I live is far superior to what I had before with a good "normal" job. My life is a dream and everyone else seems to think so also (they didn't think so when I was a successful scientist). And then again I can say that I chose not to play pro soccer because I don't like that lifestyle. Yeah, easy for me to say because I would have sat the bench. Entirely a different story for a Landon Donovan or a Pele.