I think you or we cannot rule out the fact that actually happens in gambling where most people or gamblers make gambling a place to earn, or simply they always prioritize winning in every bet, I understand that whoever it is that even though they come just for entertainment but still they will never refuse the name of victory but maybe the difference is that there are some gamblers who are too pushy to win and there are also those who wait with patience and maybe you also already know the two types of gamblers that I mentioned.
The gambler who want to earn money from the gambling site,need to increase their skill in the gambling site.The winning money in the gambling site can be increased based on their ability to make money from the same gambling site.The gambler with huge money mostly consider the gambling as the entertainment,because they doesn’t need any money to make them rich.Because they are rich already,this was the reason the rich gamblers easily increased their skill in the gambling site using their money to gambling site.The gamblers who want to multiple the money mostly take the big risk will leads to the big loss.
It depends on what type of rich gambler you are referring to, because not all gambler with huge bank roll is rich. Most people may have won money in gambling that made them high rollers, yet not rich. The rich people are very few, and not a huge number of them engage into gambling. However, the few of them who are gamblers, don't care about the money anymore. Because, as you said, they are already rich and have some money. But money has no limit, everyone still looks out for more money. And that could differentiate the rich people, into two parts. Those who still want to win big, and the other who don't care about whether they win money or not. Hence, the rich can still be in the side of wanting to win more money. Because human is insatiable. It all has to do with the gambler's thoughts and behavior. Regardless of whether he's rich or not.