if I had to guess, I might guess that it's because large (and even a lot of small) employers put profit above all else, including employee compensation. for a while, employees observed themselves working hard for zero benefit, so they simply slowed down. not everyone can just pick up and move to another job that treats them better.

if I had another guess, and I pulled from my experience as a software developer, I would say that the desire to have continuous productivity from all employees has created environments which throttle talented employees and asphyxiate those who are learning because they can't contribute immediately.

I see this all the time in my own life. I can contribute a great deal if I am left alone to do work that I see needs done, and I have demonstrated this multiple times. but if you don't understand this about me and you want daily stand-ups where I explain what I am doing, all I get is challenge from everyone on the call. "why are you doing that? we want you providing value. you should pair more." I promise, and I have delivered previously, that if you just leave me alone I can do great things, but when every last person on a call gets a say in what I work on, you render me completely ineffective, and that's where I am now. this is a direct consequence of technical leaders having MBAs and no understanding of people or the work they are doing.