Your transaction happened to use very few inputs and was during a non-peak time. Before you made your transaction we do tell you what the fee is and you do have the option to use coins with lower fee. But we would like to offer economy fee options going forward.
I think users of gambling sites should understand that there off peak periods and high peak periods indicating rush hours and times that transactions are very low. At least the charges are not the same and users can decide to withdraw at the times convenient, like during the evening transactions are lesser. Also having options of low fee coins is for users choice, we know btc and eth are usually high in transactions and so fees too get high.