Rich people do gamble always but lowkey and that's one of the major mistakes why rich people become poor again, because of greediness in gambling. You don't often see rich people gamble in public places and that's the reason why we mostly see poor people get addicted to it and lose a lot of money.
Rich people sometimes are in private places gambling with other rich people, you can't actually see them on normal casinos or any platforms, they don't like to gamble with small fishes. Why would you gamble in small stakes if you already have a lot, that's a mindset of rich gambler, they want more and that's the reason they fall down too.
You're right, another somewhat strange but valid reason is that every rich person has a fairly large degree of being egotistical and that is something that is very characteristic of most of them, so in view of this, it could be said that rich people are not opposed to playing a lot in casinos risking a lot of money, because they take great care of their money, they don't like to lose it and they know that in casinos it is easy to lose.