You have way more disposable income than a great many Americans.
Many is a fungible term. In a country as big as ours, even 10% is a lot of people.
People who are constricted by a transportation system dependent on private cars, for the most part.
That is true in many parts of the country, yes. Here in Atlanta, our public transit system is certainly inadequate, esp. the "last mile" problem. Last time I used MARTA was to go to a match at the Mercedes-Benz stadium, and, of course, I drove to the train station.
Yeah, you might be surprised to find out how many Americans need that 20 year old car,
Not at all. Some people can't afford newer. Some people just like the old cars and hang onto them.
Of course, 20 years old is 2004 model year. Power windows were very reliable by that vintage.
but don't have the few hundred bucks to invest in fixing the power windows.
Then they would not have the few hundred dollars to fix the manual windows either.
If you drive a beater, it really pays to acquire some basic mechanical skills, as well as a decent set of tools. An old car will develop all sorts of minor problems as things wear out. Things that are easily fixable, but will cost you a few $100 at the shop.
Those windows, the main cost driver is labor, not parts. Even a motor should be under $30. But you have to take the door apart (power or manual, doesn't matter) to get to it.
In an old car I had (sold it for $400 when the engine blew at 205k miles to some tinkerer) I once lost drive. Gas pedal sank to the metal. I cursed, thinking the throttle cable broke. Luckily, it just detached from the pedal, and I was on my way in 5 minutes. But how many people would not even look, and would just call a tow truck right away?
Of course, it's different with modern cars with drive-by-wire. Can't easily fix many of the problems you could in cars of yesteryear. But power windows are not that complex really.