~sniop~
Casinos doesn't want to get a trouble from allowing those people from country that ban gambling. It is a prevention from the casino but we know that those people can still visit the casino easily. Casinos can not prevent from those people so they just see the reality after those people verify themselves.
In this matter, casinos have the right to warn to those people not to use their casinos to playing gambling. But they can not do anything if those people still want to gambling in their place. Casinos still doing promotion because that is their way to grow their business. From that promotion, they will see from where people come from.
I think some gamblers do not know and that is why they would always do anything possible to make sure that they gamble on casinos that have restricted gamblers from their regions mostly when high bonus reward is attached. Many casinos also wouldn't mind to accept them due to the camouflage they used with the help of VPN to bypass their real IP addresses so casino team does not know.
When a gambler bypasses every channel that can be used to track his location, some do forget that the casino is in possession of their fund and at anytime, they can try to find out if such gambler is from a region that is restricted. This is why we keep seeing newbies complaining of casinos locking their accounts, lying about what they actually they did wrong for such even to happen.