That might be a part of it, but I think the key reason is that they solved the UI problem of decentralized casinos. The average person doesn't know what Scatter or MetaMask are, but he/she would like to play on a casino that is 100% fair.

Even if people sign-up with e-mail, an EOS account gets synced with their profile. Subsequently, everyone who plays it interacts with the blockchain without ever having to learn anything about the blockchain.