For what I know this is not really accurate, casinos pay their own taxes but they do not have the responsibility to pay the taxes of their players, so if you happen to win a big sum you need to see what kind of taxes apply to you, as there are some countries where no taxes are applied to your winnings but there are other countries in which the taxes are really high and there is no other option to you but to pay them or face the consequences if you do not do so.
Automatically, the taxes paid by the casino must also cover all types of tax costs on the gambler's winnings, because in the gambling industry, it is the provider or the casino that gets the most profit.
I've never had a big win on a lottery bet, but if I have to pay taxes on lottery winnings, I don't agree with the tax either.
If you play at an online casino, will the state also charge winnings tax?
It seems that if you play at an online casino, the government will not know about your winnings and can of course be exempt from applicable taxes.
It does not work that way, unless you were also the owner of the casino, but if that is not the case then under the yes of the law the casino and the gambler are two different entities and they are taxed individually, also the jurisdiction in which you have to pay taxes will be different as well, most casinos have a casino license from Curacao and that is where they will have to pay taxes, while a gambler has to pay their taxes at the place of their residence.