Why are the expected to carry the weight of the other 300 million?
Our largest corporation, Walmart, only pays subsistence wages. This means that after basic expenses, there is no remaining surplus to tax.
When Reagan decided to dismantle our postwar wage structure (so that our capitalists could benefit from ultra cheap labor costs), he was warned that this would turn a large portion of the middle class into virtual wage serfs with no skin in the game and no taxable income.
He ignored this, and he created trade/labor laws that allowed our noble and patriotic capitalists to shift production to more profitable labor markets in freedom hating nations like communist China. By giving capital more mobility, the result was in the form of much higher profits for a narrow group of Americans, but it caused massive deindustrialization in our cities, leaving behind an army of superfluous citizens without jobs or taxable income. And since this superfluous population has to compete with 3rd world labor markets in order to get their jobs back, they have no hope of earning a taxable surplus income.
Of course, Reagan claimed that by cutting labor costs and allowing the rich to make more money, the effect would be higher revenues for the State, which would help pay the exorbitant costs of the advanced industrial infrastructure and defense of overseas markets that his new global system required.
However, we new that Reagan was full of shit on his promise that this newfound wealth at the top would turn into higher revenue for the State. We new that the big businesses who put him in power would fund an anti-tax revolution that would result in posts like yours.
But the point remains the same. If you want the growing army of wage-serfs to have a taxable income, you have to move us closer to the wage/benefit formula we had during the postwar years when the father's factory job supported the whole family, and there was a taxable surplus remaining so that the working and middle class could greatly offset the revenue burden of the wealthy.
However, if you're going to keep Reagan's low-wage model (because you want to give investors higher returns and thereby incentivize investment), than the revenue burden will naturally fall upon the group making all the gains (that is, the surplus, i.e., the surplus that is leftover after basic expenses).