I can't speak on behalf of this specific website or any other, but I remember the pokerstar thing back in the day, it got raided by FBI so it wasn't like a small thing neither. Usually the law prohibits people from starting a casino wherever they want, so there are limited places that they can do it, however withdrawing is not limited, which means that you can deposit money to your pokerstars account from some Bahamas bank and then withdraw it to your bank of America account.
This created a bit of a loophole, which allowed people to move money from abroad to USA, which normally would be a good news right? Every nation would want money to go into their nation non-stop all the time. However it was always obvious that this would be abused by drug lords and money laundering, so that ended up being a problem for pokerstars as well. That was one website though, I can't speak on behalf of the whole law.
Yes, this is similar to the reason some developed countries prohibit such sites. Of course, it is absolutely unacceptable on the part of the state to create loopholes for fraudsters who launder dirty money. And accordingly, this is regulated by law - but roughly, a complete ban is simply established.
If we talk about BK8, - then if they have been working in their jurisdictions for a long time and are sufficiently known, for example, even here in BTT, then this means that they have resolved the issues of the legality of their activities. Well, or maybe they are being decided at the present time and I wish them to finally solve them.