Why should I not gamble when I am rich, gambling can gives you a lot of fun and that is very good for your feeling.
But you dont must play indeed with all your money, that is very bad of course, you must have borders for yourself.
Otherwise you are losing to much money and that will be not good.
If it is just fun you want, there a multitudes of ways to have that without losing money. And there ways that are more productive than just gambling. As you say, you lose money doing it. Why not, instead of gambling do sports. It won't lose you money and it is good to your health.