Andrew Carnegie wrote and lived in an era without an income tax. In that era rich men were expected to be broadly philanthropic, to steward their wealth for the good of the common, to act with generosity and responsibility. Because the state did not provide a safety net, the wealthy faced immense social pressure to act as stewards of the public good.
In today's era those expectations do not exist. The public-facing, gilded age palaces, which by their public nature tend to enforce good behavior by forcing them to physically interact with the society they profited from, have been replaced by private, gated bunkers behind tall hedges blurred out on Google Maps. The wealthy wear jeans and hoodies to "blend in" or appear common, when they are very much not. A rail tycoon in a 10X beaver tophat might offer a beggar something on the street. A tech mogul in a hoody might not even get solicited.
Income tax - and broadly speaking many other changes to the social contract between upper and lower classes, like the bureaucratization of welfare - has not just allowed but incentivized the wealthy to shirk the responsibilities of old, and outsource their morality to a (corrupt, as many have pointed out) government. And it's not good. There is no honor in giving anymore.
They can do this because we crave the dollars they have. If we suddenly, collectively, decided Elon's dollars and Tesla stock were worthless, he'd have to come out and go to the food bank.
If we repeal the income tax, virtue will return to the wealthy.
Is that something you believe?