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.