I honestly don't see any advantage for people to use VPN in casinos, I say this for the following reason, let's suppose that Duelbits.com accepts citizens from all European countries, so a person who was born in France and lives in France starts using the casino Duelbits.com and uses a VPN with an IP address from Italy, this person thinks that this is having greater probability but some time later the casino asks this person to do kyc and that person does kyc, he hands over all the documents from France and passes on kyc, so you have a verified account but continue using a VPN with an Italian address. see that the casino already knows that he is a French citizen, he has already done KYC at the casino, so what would be the point of him continuing to use a VPN with an IP from a country he doesn't live there?
First and foremost, to avoid all your logs with ISP because Duelbits knows who you are but you may not want your ISP to know you are gambling more on a particular site which can lead to possible physical threats.