He has the skills
Anthony Curtis has the ability to support himself quite well as a casino customer. He also has the ability to support himself quite well doing things other than bucking the casinos. Curtis is making rational decisions as to how he uses his time. There is more upside potential in doing things other than trying to beat casino games. Curtis is willing to invest time using his blackjack skills to earn money, but only if his hourly expected win rate is high enough.
Curtis is not unusual in that regard. Many of us have the skills to win money at blackjack, but also have other enjoyable ways of earning money. If a casino wants us to demonstrate our blackjack skills, all it has to do is pay double on naturals for bets up to say $500, or something that has equivalent EV. Then you would see that, yes indeed, Anthony Curtis is a professional blackjack player.
Stanford Wong