Casinos have to do KYC (Know Your Customer) checks for several reasons. Firstly, it is a legal requirement in many jurisdictions and failure to comply can result in heavy fines or even the loss of their license. Secondly, it helps to prevent fraud and money laundering by verifying the identity of the player and ensuring that they are not using fake identities or stolen credit cards. Finally, it also helps to protect players by ensuring that they are over 18 years old and legally allowed to gamble.