Well perhaps leaving your crypto on a gambling casino wallet is still good for a short period of time like a day or weeks, beyond that --that is too risky.
The problem here is that you don't know when a hack will happen. So, it doesn't really matter for how long you leave your cryptos on the casino. But, surely, the shorter the less risky! (
not your keys not your money).
The goud thing, though, is that the money used for gambling is supposed to be a money you can afford to lose and you are supposed to be aware of the risks involved.
On the other hand, I believe securing customers funds is mainly the responsibility of the casino. The least they can do is to have a hot/cold wallet setup. This way even if they get hacked most funds will remain safe and it won't result in their bankruptcy.
If the money we have in the casino is not too big, then maybe it will be felt by us but some gamblers leave a lot of money on the gambling table because they think to use that money to gamble at another time.
And when a hack occurs, their money can be lost to be taken by that hacker but if the casino has the money stored in a safe place, it will not be a concern for them because their money is still safe.
Yes, it would be better if we only use the money we can afford to lose, regardless of whether it's a hacker problem or losing because of that money we use to gamble.
So having a cold wallet for a casino is recommended because that can prevent hacking that can happen anytime.