Here's the thing, if you are John and start to gamble, would you bet with high risk (betting with huge amount, betting in low chance of winning, etc)?
If I was in the situation of John I would pick a game where it doesn't purely depend on luck like sports betting. If I'm lucky I can even recover my capital. I would bet it on the NBA where for me is more easy to predict the outcome of the game than other sports. I will analyze the players, listen to some analyst or just bet on the more popular team.