That's a better thought, than finding a bug and abusing it would be a crime and would harm other people. Better to report it straight away and maybe get a bounty commensurate with the bugs found.
But if there are no prizes, then a casino like that should be taught a lesson. At least if the bug is critical and could jeopardize the user's funds, the payoff might be thousands of dollars,
And if there is no bounty, it will be up to each user who finds the bug. But they must be aware that what they do with the bug will impact their gambling account. Someone may try to use the bug first and withdraw the money if he can. But it's also possible for someone to directly report a bug to the casino so that the casino can fix it right away. And it is up to the casino what it will give to the person who found the bug but at least, the casino can give a thank you gift for helping to find the bug.
There will probably abusers who will take advantage of that bug prior reporting it. Though it is risky because it might really affect your account. That's why it is really better to report it right away. For the reward of finding the bug, well, gamblers should not have expect, as we all know, if there's a bug casinos have a huge loss
Mostly if the bugs are in existing accounts only, they won't really be exploited because you'll be suffering for sure. You are right, it is better to report it immediately with the help of the casino and also hope to have rewards on it, but if this is the case, the casino won't be giving any amount to a user unless they are very generous. Mostly those bugs that were exploited are on new accounts or even without it, which is why bug bounty hunters are finding them and seeing if they can get rewards from them, or worse, if they can't get any.