My personal (purposely incomplete!) answer is because the whole world doesn't deserve to be rich. Imagine this scenario to help understand why: Let's say the top richest people gave away so much money that every person on earth was a millionare. What would happen? People wouldn't change their spending and other habits, in fact they would buy more useless stuff. Prices would thus rise and rise until they matched the n…
As mentioned in other comments, you can't escape scarcity. If everyone became a millionaire overnight, would there be enough mansions for everyone to buy the next morning? How about PS5s? How about steaks? It's wishful thinking and politicization to pretend otherwise.
Some things are artificially scarce, like diamonds. Other things are made to be cheap and disposable like clothing so you’ll buy more in the future. And other things are made proprietary so that you’ll have to buy multiple of the same thing.
A simple example of the last point is modern consoles. PS5s and XBoxes are basically PCs at this point. Yet they are made to be incompatible and minimally upgradeable.