The people who have lot of money can be a good gambler because they won't get much life problem even if they lose money in gambling so when you want to gamble make yourself rich.
Having a lot of money does not guarantee that it wont affect their life, once a rich people get addicted to gambling and get very bad luck continuously then it will affect their life obviously. Good gamblers are depending on how much money they have, it is more about how they can manage their money while gambling. Rich but unable to have good money management in gambling = bad gamblers.