If not that some of these casinos don't know how to handle data and users information, kyc actually help limit abusers from using the casino the way they like and if reduce cheating. Unless you are a pro in cheating, if there is a KYC verification in a casino, you wouldn't be able to cheat the system but just like I said some of these casino sell users information which is very bad thing, you don't know if they even follow data protection policy.
With the many casinos that are indeed developing, it is possible that there are indeed casinos that have a bad reputation so that their goal is data or money laundering with the KYC required of their players, so we ourselves must be smart in choosing a casino because of course we ourselves do not want to experience any problems.