Because when you say "oh I'm happy with Bezos and Zuck having over 100 billion when I'm lucky to put food in my kid's mouths" you are going to revert back to the monarchy, we need to continue to fight these people who think that the rich should continue to trample the poor, especially the really poor of the world. I have no problem with an upper crust, but currently we're moving back to just a few people controlling the world, politics, and freedom.

If human nature wasn't greedy, vain and materialistic, the modern economy would not exist.

And if pithy comments didn't exist... we'ed have to accept that no single thing, or small cohort of factors decided the overall trajectory of society.

Wealth, and power carry a social momentum. Antipodal to that is the high amount of frictional cost associated with change at scale. Those properties of our current economy effect what change is possible and when.

The modern economy exists in this unequal hodgepodge for the same reason some animal look alien to you, because it was not planned. Unfortunately for us, unlike animal evolution, the rate of change of the economy, tech progress, political winds, and all the social tendrils that stem from that unholy amalgam grow rapidly and defy organization.

You can call it the expected end result of human nature if it eases you. But. to me, it looks like a problem looking for some good engineering.

Are you arguing that if we take away the bad parts of human nature, the economy would collapse? What useful function does greed, vanity, and materialism serve in the modern economy?

I am arguing the economy would change and probably look nothing like it does now. Market economies basically have taken the "bad" aspects of human nature and use them to drive price discovery, demand creation, and efficiency gains. There would be other ways to do these things, but working within the bounds of normal human behavior has it's advantages. The economy can function on "whatever works" not just our better angels.