I think people that play casinos already know that the odds are stacked against them. The urge to win, despite the odds, gives them something to shoot for that they aren't supposed to have. In essence they are hoping to steal from fate.
It makes as much sense as people that say their credit cards are robbing them with late fees and high interest rates. And yes, sometimes credit cards do surprise you with untold (but still printed) conditions to the agreement. O.O
But casinos in FFXI, for the most part, are very easy to understand and hopefully run in a fair way despite the odds against the player.