i saw a post here once asking about whether banning gambling will actually solve some problems. well even with gambling deemed illegal, it has not completely disappeared from a country. for example, in north korea gambling is illegal for its citizens.
but there are still gambling events that take place most often organized by some authorities or really rich and powerful people. i guess that making gambling illegal is just a way to make it less accessible to the general public but the rich always finds a way.
there was even a case where north koreans are targeting foreigners and selling them their own made gambling platforms.
North Korean IT workers created and sold thousands of illegal gambling websites to South Korean criminals to raise billions of dollars keep in mind that gambling is also illegal in south korea. so my point is, everyone eventually finds a way.
I wouldn't even bother talking about what's illegal or legal in North Korea, they are the most isolated bubble country on the planet and a pure anomaly. Banning gambling in most other countries that are not hyper oppressive is generally doomed to fail, especially with the internet, because people will find a way to do this form of entertainment. There are plenty of ways to have fun in life without gambling, so it's not exactly a life or death situation if it's unavailable, but it's usually banned because of religion. As you say, rich people are not constrained by the laws of one country because they are hyper mobile and will either relocate their citizenship or just travel abroad if they want to step foot in a casino.