Why can the federal government tax money that can only possibly be in my pocket if I've committed tax fraud against my state?
If I make 100K and my state takes 5%, I now only have 95K. There's no option for me not to pay 5K to my state.
(and no, for most people uprooting yourself for tax purposes isn't a tenable option)
Now, I have to pay the federal government. Why should I be on the hook to pay taxes on 100K in income, when I truly only earned 95K?
With sales tax, you could theoretically not buy things subject to sales tax. With real estate tax, you could in theory just rent.
Yes, in practice it's not like taxes are so punitive that > 100% of my income will be demanded, but it seems unfair to levy such taxes.
This assumes, of course, that the state has the first dibs on a person's income. I'd be just as happy if the federal government amended the constitution saying that all states levying income tax must deduct federal taxes paid from taxable income amounts.