I wasn’t that deep into it during those times and didn’t fully understand what was going on, but I’ve heard that this exploit caused real losses for some platforms. That’s probably why most casinos today require at least 1 confirmation before crediting your wallet.
Not only that, nowadays, because of those kind of exploits which abused the well-intention of casinos to make deposits immediate, now casinos only access coins and tokens from blockchains with high enough volume, liquidity and security, so there are not risk of them losing their funds due to 51% attacks (as it would be possible to happen with coins like Ethereum classic). Actually, because of the 51% risk, I have not seen so many casinos giving to support to Ethereum classic.
Interestingly enough, I have seen people (who are enemies of decentralization) to point out at double spending on the Bitcoin main chain as a reason to completely avoid investing and holding Bitcoin. Which is silly.