I hear that sentiment a lot, but it doesn't seem right to me. My salary is pretty close to the median plumber's income, and my family's effective tax rate last year came in at... 1.6%. And that's with all retirement account contributions going toward Roth accounts. If we'd chosen to contribute to traditional IRA/401k accounts instead, the EITC and child tax credit would easily turn our tax bill negative.
It might also result in even more spending. I don't think that there is any "natural ceiling" when it comes to willingness of politicians to spend other people's money. The only ceiling is external - how much will the system bear.
I suspect you're using a different definition of "income" than the IRS. What is it?
For one thing, many plumbers do make it to the 1%: Trades are a profitable line of work for the industrious.
But the median 1%’er is paying 3-4X the effective rate of the overall median earner.
You have conflated the tax rate with the tax amount.