My current guess is that it's because of the increasing institutionalization of society, >which is caused by economic growth. When your tribe is made up of a hundred >people, you can model each person in high detail when you interact with them - >taking into account their personality, their strengths and weaknesses, their past >interactions with you, and so on. However, in a corporation with a hundred thousand >people, the CEO doesn't have time to construct complex models of each worker, >and yet he must ensure that all the workers cooperate effectively. How does he do >that? By making each worker simple to model - by constructing a set of rules which >governs each worker's behavior, and constrains them to behave in simple, easily >understandable ways.

That also sounds a lot like what a nation-state has to do. And that's been going on for thousands of years... What's democracy but basically taking a bunch of tribes, having them select their representatives, who then become a supertribe who also elect new representatives until you have a small enough bunch of people so they can work together?