Lightening network is not what much casinos are in a look after and same is applicable to the gamblers as well, using a lightening network is by far a better option as long as the conditions warrant such which will help the payment system more faster and to cover as mny as possible transactions within a shortest time but users will always prefer using their altcoins in gambling because they have some varieties of them which are mostly supported by the casino they use.
Plus there's a hidden "feature" in using the Lightning Network, "in theory". It's also an off-chain layer not just for faster, and cheaper transactions, it can help with your privacy too. Because if you send yourself a transaction, your transaction in Lightning takes multiple hops, and you receive outputs that are not connected to those UTXOs you sent.
I believe that's one of the "hidden reason" why there's so much disinformation, FUD, and gaslighting regarding basic information about Lightning. There might be entities that don't plebs like us to use it.