Because direct collaboration scales as O(N^2) in terms of person-to-person interactions which becomes rather big as N grows. Having everyone spend 80 hours a we

Because direct collaboration scales as O(N^2) in terms of person-to-person interactions which becomes rather big as N grows. Having everyone spend 80 hours a week in meetings and still only understanding 1% of the business seems a silly use of time and rather inefficient in actually getting things done. Thus you get managers who are the ones in meeting with other managers which leads to a smaller N.