Most times the details provided during the KYC are kept private without the interference of a third party. And most of this details are used to prevent money laundering or any financial theft through their platform.
But I see no reason , why someone with a clean heart and intentions be scared a d worried over KYC?
Almost impossible, but not impossible at all, we still having some casinos like Just-Dice who allows multi accounts, bots, and they never ask for KYC. If you use the alts or the bots to try to damage the site, they only ban your account, but even banned accounts are allowed to withdraw. I would say is the last one of that freedom casinos types.
From my point of view casinos shouldn't hold the uses money for KYC, but we are playing with their rules. It's how it works nowadays.
Nonetheless, KYC is important especially when the company is operating from a sane country that does not take money laundering lightly.