We could start by taxing capital gains progressively, similar to salaries. In my country, you pay a flat 25% no matter if you make one dollar or a billion. Why

We could start by taxing capital gains progressively, similar to salaries. In my country, you pay a flat 25% no matter if you make one dollar or a billion. Why should a worker have to give away up to 50% of their salary when people with capital only have to pay 25% tax?