Tl:dr If Americans aren't making more money Bezos can't raise the price of Prime and Amazon loses big on revenue.

Look, I don't care about someone's motivations as long as their actions are good. Jeff Bezos didn't raise the minimum wage of all Amazon workers to $15/hr out of the goodness of his heart, dude's the biggest opportunist squeezing efficiency out of human beings themselves, Jeff Bezos raised the minimum wage in his company and wants the Federal Government to raise the minimum wage to $15/hr because no one has the money and willingness to stay with Prime if there's another price hike.

The American economy is at a weird point. Stock market is at an all time high, borrowing interest rates are at an all time low, inflation is steady, and worker's wages are not rising. This means people have less money, less buying power, and less motivation to buy stuff in general. With wages stagnant, people are squeezing value out of every dollar they make.

In Jeff Bezos' ideal world, Amazon Prime would be $179/yr, which averages out to $15 a month, up from its current $119, which averages out to $10 a month. So while Jeff Bezos keeps and keeps adding value in Prime in the form of original video, Whole Foods perks, delivery perks, and so many other things, unless Americans are both able and willing to afford a price hike to Prime, Bezos knows that it doesn't matter if Prime offers all the value in the world, people will not pay for it.

Or maybe I'm giving Bezos too much credit and he really did just cave to public pressure due to wanting to be liked, which is one of the motivations for that whole Amazon HQ2 shitshow.