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.
Your words contradict themselves: you say that rich people don’t mind gambling in casinos, risking large amounts of money, but they do this because they are very careful with their money. I disagree with this. If you are careful with your money, you would never risk large sums in any kind of gambling situation, including casinos.
If you are truly careful, you either wouldn’t gamble at all or you would manage your risks in a way that focuses on preserving your money. I believe that wealthy people are mostly like this, because otherwise they wouldn’t have been able to achieve the fortunes they possess.