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.
Rich people have a good source of income to fund their gambling. Most of them just use gambling as stress reliever so even losing some is already fine with them because they can easily earn it back while they have some fun on their free time.
They use gambling the way it was intended which is source of fun since most of rich people doesn’t have a legit social life due to their business or work habits.
Aside their value their money, they have huge funds for them not to cling on gambling to win more.