Just to clarify this point, the income tax is progressive and affects the rich more than the poor on income. A software developer making $150k will pay 24% on additional income while someone making $30k will pay 12% on additional income.

The distinction in the US is whether you make your money through labor (max 37% tax) or capital gains (max 20% tax). There is a lower tax rate for capitalists (who make money via ownership of capital) vs laborers (who make money through labor income). Furthermore, capital gains can be delayed until you realize your gains (sell your capital). This distinction is what practically gives the rich lower taxes than the poor.

All this nonsense should be rolled into a single income tax and then the overall tax rate should be lowered. Yeah sure there might be good reasons for a low capital gains tax but if that is the case then there are good reasons for a low income tax as well. The only thing the income tax should be doing is discourage employers from piling up all the work on as few people as possible.

Employers prefer keeping people full time and full time unemployed because it is more efficient per worker and the bargaining power of the unemployed doesn't exist. If everyone were to work according to their own demand for labor then this bargaining power cliff wouldn't exist and a whole lot of welfare programs could be abolished.