Because politicians sell progressive income taxes as a way to screw the rich, when it actually just screws the upper middle class, since the actual rich don't have jobs to tax the income from.
There are many people making over $200,000/yr. With 20 years of investing $150,000 of that, it's incredibly easy to have over $6.5 million. I don't see why it can't be a two-pronged approach with both higher income taxes and wealth taxes. It's what was done in the 1950's, and there was still plenty of wealth then.
That time period was one of great prosperity that won't be repeated. Market returns were higher; most of the low hanging fruit has been plucked, and you can expect ~5% in equities returns. Its going to take far more capital now to get the same returns your grandparents had, which is why you see capital chasing returns across the world.
https://www.cnbc.com/2017/05/07/get-ready-for-dramatically-l...
"The leaders of Vanguard Group, overseers of some $4 trillion in client assets, have been advising investors to expect a typical 60 percent stocks/40 percent bonds portfolio to deliver two- to- three percentage points less in nominal annual returns than its long-term norm. (Since 1926, such an asset mix has returned better than 8.5 percent annualized.)"
"Other forecasts are even less generous. Research Affiliates, a quantitative and "smart beta" fund manager, projects that U.S. stocks might only offer one percent a year for the next decade, after inflation. This is based largely on the so-called Shiller P/E, a ratio of the S&P 500 index to its trailing ten-year average earnings, which is now above 29 and higher than any period aside from the run-up to the 1929 and 2000 market peaks."
"And with risk-free 10-year government debt yielding a skimpy 2.3 percent in the U.S. and far less elsewhere, all other financial assets have repriced for skimpier future returns as well."