The 12 million men & woman that served in the military in WW2 came home, the GI Bill sent vets to college, and they started families. This created the largest, most vigorous and the best educated middle class, in the history of the planet. Labor unions were at the zenith of their power, our eductaional institutions were the envy of the world, corporations made money, the wealthiest made money. The American Dream was born.
A Middle class is a rare thing, occurring only 3 times thru-out history. The first rising of a middle class occurred as a result of the Black Plague. The Black Plague killed about 30 to 50% of the worlds population, creating a labor shortage. This allowed that Trades & Craftsman to command a higher wage, which trickled down to the common yeoman, much as the unionization of US labor in the middle 1900's allowed non union labor to command wages akin to union labor. Some have written that the Renaissance, without a middle class that had the leisure time to even consider art & music, let alone the time to paint, sculpt, write & perform music, would have never occurred.
The second rising of a middle class occurred in the US colonies in the middle 1700's. Once a few Indians were driven away from an area, there was free land available for farming. In an agrarian society this was a big deal in that you could own your own land, grow & sell your own crops & keep the profits, much as a family owned business does today. One could take care of its own.
The third rising of a middle class occurred during the Great Republican Depression of the early 1930's. FDR's New Deal brought forward tax progressivity, as well as labor rights earned thru the union movement, such as the Child Labor laws passed in 1937 & 1938, as well as Education rights under the GI Bill, for returning Vets.
The real point of progressive taxation is not producing more tax revenues, the point is having a large and vigorous middle class that can participate as citizen legislators,& send its kids to college, so those kids can invent lots of cool stuff for the corporations to make money off of. Consider kids as assets. How do you make best use of those assets? Educate those assets of course. Regressive taxation taxes the Middle and Working classes out of the economy, Progressive taxation engages the Middle and Working classes in the economy and are better to take care of their own. This means a more stable family.
Enter Ronald Reagan and the start of full spectrum warfare on the middle class. The opening salvo, the PATCO strike. Busting the Air Traffic Controllers union was the start of a multi front military style operation to drive wages down for all Americans. Then we were told that Social Security was going broke, this represents the opening of a second front of the War on the Middle Class that resulted in the doubling of payroll taxes.