One thing that can't be codified in procedures is what I call "situational awareness" for lack of a better term. I don't think you can learn how to work in a machine shop safely from a book. Or recognize when a complex design is heading towards being unworkable. In my organization, the older engineers have a sixth sense for projects that are going to be cancelled.
There's a reason why older drivers (up to a point of course) pay less for car insurance, yet the rules are the same for all of us.