Why should a truck driver or nurse pay a 28% tax rate, but a very wealthy person pays 15%.?

A billionaire pays a 15% tax rate when he makes 20 million dollars by buying and selling a stock within ONE YEAR AND TWO DAYS.

A truck driver who works 60 hours a week and makes 100,000 or 90,000 after standard deductions pays a 28% tax rate.

Why do working class people pay 28% but billionaires pay 15%?
Update: There is no loophole needed for the 15% tax rate on capital gains, it is law.
And yes, why should a truck driver be punished by paying 28% for his line of work, and a stock trader pays 15% for his line of work...the income is the same.
Update 2: 4e4a, did you know that profits from stocks held one year and 2 days are not ordinary income but capital gains income which is taxed at 15% by law. Your chart is irrelevant.
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