TL;DR: People retire, make sure they document what they know in any medium. Also make sure new hires go through the documentation.
Seems like common sense.
Seems like common sense.
I thought it was just something startups struggled with, but my mom, a long time transportation engineer, was just telling me about consultants who were paid a ton of money to do toll road analyses for the state and left sparse documentation, so I'm guessing it's a struggle everywhere, though some are better or worse at it.