I personally grokked it when I was writing up some peer review. I thought I was making a compelling case: I showed where he had solved a tough problem, how he worked through problems, resolved it and thought I was establishing that the guy was on an upward trajectory.
My manager kicked it back and was trying to explain what he needed. We went back and forth, and finally he said, "look, I'm going to be in a room full of other managers, and I need ammo to get Chris a promotion."
That was when it clicked. I had learned persuasive writing in an environment where it pays to spend a lot of time making your case. But on a promotion board, there might be a dozen managers trying to get a word in edgewise, so they need to make their case with simple, unambiguous facts.
So it's a matter of it being a writing style that meets a specific need, and which engineers aren't trained in.