I am not concerned with money laundering in this context. Held people accountable is a problem of the casino as business, not really mine as such. Accounts can be restored by other systems. They do not reduce addiction, just send it somewhere else. Enforcement of local rules is not really my problem, it is the law enforcing authority.
Overall, the only good reason is to reduce tax evasion, which I am not sure is "good" in all cases.
Normally I try as much as possible to avoid that route and if I can go all out without having to give out my personal IDs and other numbers that can be used to trace and tax you on several things is why most of us rather play in online casinos that accept cryptocurrencies which give us the 100% privacy and other security, although the government may want to exact tax from the citizens through the KYC which will be used to trace citizens income.
So aside from the government, KYC of of no benefit to either the casino or the gambler, so in the end, only the government benefits from the KYC mandatory, no wonder KYC always comes from licensed casinos that are regulatory compliant.