The casino is providing value in the form of entertainment. That is what is being paid for.
As for gambling being the best use of crypto… That’s more a sad result of this community and the lack of supporting talent here than anything else.
Casino - yes. Like any business that people voluntarily bring money to, a casino gives them something of value in return. Not only entertainment, but also a certain social status (especially if it is an expensive, luxury casino).
But what does the person who wins at a casino get paid for? What value does he give back? What did he do to earn that money?
If instead of money he receives cryptocurrency, that is another story. That is not very different from ordinary airdrops or Bitcoin faucets (remember those, back in the day?).