Maybe for entertainment purposes but I can think of alot more ways a rich person can be entertained than only just gambling in this day and age to be pleased in doing something else other than that.
After you're rich, you are seeking for power. Think of the billionaires - Zuckerberg, Gates are billionaires. They're rich enough to live a hundred lives off their money. Why aren't they just closing their business and living off their money???
You can't just sit down all the life doing nothing - you need to have something to do. For them, it's getting money. Riches do gamble too.
Still putting that aside if they have nothing to do then just go to the poor countries and help repair the world. That would seem to make them feel like Superman unless they like the feeling of evil power that gambling offers as a cure for that emptiness that they seek so badly.
Well, I think they are not closing their business because it is not just themselves that are feed by their company. Even if they are rich, I don't think that they will consider gambling when they have nothing to do, issue was right, it is good if you would just help those in need instead of losing your money to those greedy gamblers, be like a philanthropist, they are into the result of their deeds and not for the reason..
But with having so much money in your disposal why not just try and make a better world to live in and spend this money fight drugs and prostitution in their parts of the world?
What ever happened to that Mexican cellphone empire guy that was the richest man in the world two years ago? He should of used that money to fight all those drug lords and cartels in his country.
Then Trump wouldn't be all mad at them for cause so much grief to America and then trying to build a Super Wall to keep them them out of the States.
I think this is kinda off topic - drugs in mexico from op's question whether we still gamble if we were rich.
If I am rich though, I think I would still gamble - this time with higher bankroll and many sessions to cover loses. However, I will not put all of my attention in gambling, I will instead do some charity activities and help the people that are in need.