i think not all crypto related gambling sites are blockchain based . some gambling sites accept cryptocurrency as payment and you will still need to pay for the transaction fees before you send your funds into your gambling account and the fees will not always be expensive but it also depend on the price of cryptocurrencies . i think blockchain based casinos are more fair .
I see no reason to create a casino based on the blockchain for betting.
Using cryptocurrencies to make payments is an excellent solution, but for direct betting, this is an excessive waste of commission fees. Much better to organize everything based on the database.