Because people being self-disciplined and self-motivated annihilates the management layer. What do you manage when people manage themselves? You can be a project manager or you can be out of a job. They don't like that.
I'm not a manager by title, but when I'm managing something, my objective is to get as many hassles out of the way as possible and reduce as much cognitive load off people as I can. The rest usually takes care of itself.
Sure, if the managers have any experience at all doing the actual work. These days that is rare, middle management are all just MBAs who don’t have a clue how to do the work.
I have actually been a manager at a big tech and a small start up, and yes there is politics at all sizes, but its extremely rare for an engineering manager to not have been an engineer previously. I was that manager, being the mentor.
Those are the managers that hate work from home. Not managers actually doing productive management.