That's because it's an income tax, not a wealth tax.
Too many folks have been brainwashed into thinking that the Federals tax the wealthy (those who already have wealth) when in fact the Federals tax those who are trying to become wealthy by generating income, particularly non-investment income such as wages and self-employment income.
In other words, the bastards with money are using the Federal (and to some extent, the various States') tax codes not only as a means of keeping people from accumulating wealth but also manipulating their behaviors (through the carrot-and-stick system of deductions and credits).
But as you said, the IRS code punishes those trying to gain wealth while rewarding the very wealthy by only taxing income and not taxing consumption.
And on top of that they allow very generous deductions in income produced by politically favored investments and sheltering income and benefits from “IRS Approved†foundations. See Bill Gates and Warren Buffett. They have avoided both the regular income tax and the Death Tax entirely via trusts and foundations designed to provide a continuing source of income for themselves, and their heirs for generations to come.