I recently worked for a telecom and they had an unspoken policy of cycling out techs and engineers with regularity. I cannot count the horror stories where a handful of semirandom firings caused a system that hundreds of people relied on to meet productivity quotas stopped functioning within weeks due to the semirandom person being fired being the person that ran the system.
They spent millions of dollars a year constantly rolling out replacements for these systems that were always without fail worse than the ones we had because the vendors they threw this money at weren't building specific use applications for a single business function and it seemed like every new app had a wiki function, a chat function, and a smartphone app when all we needed was a way to look up a coworker's permissions or update a ticket.
Tribal knowledge cannot be evenly distributed in a business system because not everyone in the business system needs to know it. The mail person does not need to know the CEO's advertising strategy. But in an ideal meritocratic system the CEO would know the mail person's contributions to the system and wouldn't replace them with (for instance, a series of air tubes) if that mail person was considered to bring warmth and happiness to the people they interacted with, providing value far in excess of their letter-distribution capacity.