Lightning Network is not yet developed enough to adapt to online casinos. Several factors are depending on LN.

Though transactions fees are near around zero but there is a matter of opening and closing a channel between two parties you can't open/close Chanel in off-chain you must have to do that in on-chain so it is costly. Opening and closing channel multiple times is costly and until you close the channel no partis won't get control of the funds.

After opening a channel both parties have to deposit the same amount of bitcoins in a multi-signature wallet to make a pool, then you can exchange bitcoins for each other via off-chain from the pool without any cost. for doing this both parties have to be in online with their private keys and there is a matter of privacy. (insecure)