Without poor people, who's going to cook your fast food? Who's going to manufacture your electronics?

Sure, those people could unionize, demand better wages, and improve their quality of life, but that's going to increase the manufacturing cost of whatever goods or services they produce. And if everybody does that then the ratio of purchasing power evens out to the same as it was to start with, because all goods cost more in order to pay the workers who made them more, and the rich will skim off the same proportion of the cost.

The exact numbers are irrelevant. It's entirely about proportions and hierarchies. The rich will make sure that the poor stay poor. The only way to lessen this disparity is to bring the rich down.