I think this only looks true on a local level. It's easy to see why Jimmy pulls ahead of Johnny when Jimmy's working more diligently, but they're starting from a fairly even playing field.
A lot of the big cards are just dealt to you. Your parents, your skin, your religion, your school, your intelligence, your health, the neighborhood you grow up in--these things have a huge impact on what you do or don't have to overcome once you're old enough to take responsibility for your choices, and you don't get to pick them at the start. They have an outsized impact on what you even believe to be possible, never mind what you think is normal.
These are the times I wish we had a life simulator because I think people would really start to understand just how many advantages they have and the ways they contribute.
It's like how everyone says they would be anti-slavery if they grew up before the civil war despite the numbers just not supporting that. If I took away your advantages and made you do your life over you probably aren't going to break the mold and will end up roughly where everyone else of similar life circumstance ends up. What special spark could you even have? Because hard working and smart people are born in all walks of life but that only takes you to a local maximum.
You start having to consider that maybe white people are actually the superior race if you truly believe that it's not privileges because how else do you explain the vastly uneven distribution of success in the US?
No, I'm saying that on a population level, it's rational to assume the luck of the circumstances you're born into, on the whole, is likely to be reflected in your average income over time, and while it's a blunt tool, taxing the people on the higher end more than the people on the lower end is one way to try to mitigate the influence of that good or bad luck and level the playing field.
A lot of the big cards are just dealt to you. Your parents, your skin, your religion, your school, your intelligence, your health, the neighborhood you grow up in--these things have a huge impact on what you do or don't have to overcome once you're old enough to take responsibility for your choices, and you don't get to pick them at the start. They have an outsized impact on what you even believe to be possible, never mind what you think is normal.