Decentralized casinos do exists, they are the dapp versions rooted from certain coins, right now the most known one is eosbet which is a decentralized casino and right now they basically have dice only (they have crash and baccarat too but I really think dice is what draws people to their website). It is not a "casino" perse but they are really getting there.
There are other examples too if you check the dapp world and see but they are basically the same except couple of trust issues removed, after all if you trust your dice website than decentralized is not really important, for example I trust primedice enough that its basically as trustworthy as decentralized for me, same with stake too. So all in all it all depends on what you are looking for but they do exist out there if you look for it or at least google it.
Recent days in the gambling network we haven't got much of dApps. Eosbet is the one that function on the blockchain platform while most of the gambling websites we use now were much into the centralized service with cryptocurrency acceptance. Blockchain into gambling is a complicated process which is quite hard to develop without flaws.
Most lottery with cryptocurrency acceptance marked its entry and those were promoted with the smart contracts network as the lottery service render itself had their own ERC-20 token. As gambling doesn't require more of regulation same as that of the exchange services we can expect the future of casinos to be fully on blockchain to enrich effective functioning.