Why shouldn't wealth be displayed?
Imagine your relative is in a desperate situation and needs 1 million. He knows you have tens of millions, so he might resort to moral coercion (or worse, directly kidnapping you), as he has no better options. This is the most convenient method he can think of. If you lend him 800,000, he will hardly feel any psychological burden, because for you, 800,000 is just a drop in the bucket. Even if he does not repay you, you won't become poor from it, and he won't be overly grateful to you.
Even if you give him 3 million, it won't lift him out of poverty; he will think it’s quite normal. If he had tens of millions, he would easily give you 5 million without blinking, and you only gave him 3 million, which clearly isn’t enough. He might console himself, thinking that not everyone in the world shares his sense of conscience and loyalty.
Now, suppose he doesn’t know you have money. If you lend him 300,000, he will be extremely grateful, treating you like a great benefactor. You could even pretend to scrape together some funds to help him reach 600,000, and from then on, his life would be yours.
This illustrates the difference between giving control to others and keeping it for yourself.