The problem is not only waiting but for how long he should wait. As the hours and days pass by the frustration increases and at the same time, OP might think the site may scam. The best solution would be that the support should look at this case and reply to him that he should wait for the tx confirmation. This way he will be relaxed as it is only the matter of transaction being confirm and no manipulation of scam by the site. This way he will be relaxed as it is only the matter of transaction being confirm and no manipulation of scam by the site.
That's true but it's not casino's fault and I'm more than sure that if OP contact support as he said that he did, they will tell him the same: Wait for the tx to be confirmed.
Since he already knew it from his first post, he should have been relaxed without saying anything.
Anyways I guess OP's want to express his curiosity about the reason behind this rule and why (a lot) casinos apply it.