OK, here's your answer, as simplified as I can make it based on your premise:
Because the guy with the net worth of $100 is unable to contribute to the economy. He is too poor to pay taxes, he's too poor to buy food for his family and therefore has to rely on government help to feed his children.
Meanwhile, the rich guy with the net worth of $5000 has used his immense wealth to manipulate politics and has a sneaky accountant, so he also pays practically no taxes, compared to the middle class.
So it's up to you and me, the guys with a net worth of let's say $250, to help out the poor guy with the net worth of $100. But that $5000 guy is cutting our jobs and shipping them to india, so we have an ever shrinking population of $250 net worth people, and a growing segment of $100 net worth people, since the only jobs available are minimum wage.
Following me so far? With less and less people buying socks and shoes and food, and paying taxes, the economy shrinks. Meanwhile the very rich do not go to walmart and buy 10,000 pairs of jeans, so their contributions to the overall economy are minor compared to their immense wealth.
Please see the documentary "Inequality for all", you can find it on netflix streaming, and it will describe it a way that everyone can understand, even Fox News watchers.