> The second effect is related to the fact that companies usually target older people with expensive jobs. In an a big org these are the wizards who have the unwritten cookbooks in their brains. When they leave en masse, a lot of the organizational memory is gone, and expensive operational mistakes of the past are forgotten. These have longer effects that will haunt the company for many years.

This can be a good thing. In my experience these people are generally unambitious people whose stand out by holding a job for a long period of time, not in any innate skills.

In orgs where they're valuable, they're a symptom of a failure to simplify systems and share knowledge. And when you have a majority of seniors who's only value is in being a well of knowledge, they're highly motivated to perpetuate that anti-pattern.