When the casino starts asking KYC the gambler who stays in the country where gambling is illegal will learn the difference. No difference at all and he will be banned instantly when they see the documents he is a national from a country that bans gambling.
But because some casino allows gamblers to withdraw certain amounts without KYC, the VPN users are fine. Once casinos ask KYC regardless of how much you have in the account, I guess users from those countries will start to be lesser and lesser.
I think we have three scenarios here that should be taken into account by the gamblers when it comes to the gambling sites and the VPN usage.
1) If the gambling site prohibits the use of vpn, DO NOT USE VPN
2) If you live in a region where the gambling site is does not allow you to play, DO NOT USE VPNN to bypass the restrictions. As once you are caught the gambling site may block your account without refunding any money in your account.
3)If the gambling site allow the use of VPN and you are not in the restricted country, you may USE VPN to bypass the local ISP detection if your government prohibits the general accessing of all gambling sites.