A long time ago, some MBAs decided that humans were basically interchangeable, and the problem was that companies just weren't documenting their internal business processes well. Once those processes were documented, then cheap labor could replace expensive experienced employees.
Note that this idea came from a bunch of people who contribute nothing to society and have zero inherent talent at anything.
So, companies bought into this and started documenting random things and firing all their best paid workers. That was uniformly a disaster, but the zombie concepts live on just like trickle-down economics.
The institutional knowledge that leaves when a trained, productive employee departs is the destruction of a valuable asset (sometimes the transfer of that asset to a competitor) - may as well just light money on fire.