The "millionaires and billionaires" that the left ostensibly hates do not make their money through income or corporate bonuses. Individuals like Nancy Pelosi (who bought LEAP calls on Zoom in 2019, how convenient) make their fortune through capital gains.
We COULD have a more equitable society if we raised the capital gains tax.
Raising the income tax only hurts the upper-middle class and lower-upper class, effectively creating one giant middle class and one tiny legacy class.
First, all taxation is theft. Some talk of double taxation, but that isn't this.
The concept of low-to-no capital gains taxes dates way back to when saved money ("capital") was used to start business and generate production and jobs. The initial savings/capital came from work. Investments deriving from that capital investment were beneficial because they fed the business productivity cycle and were to be encouraged.
HOWEVER, the FED prints free money and the banking system has totally negated the concept of true capital investment and now punishes savings. Therefore capital gains are now simply income that the "correct" people earn rather than those other people. The "correct" people are being magnanimous (virtuous?) in allowing us to partake a little bit in their tax-reduction tool.