Why are our responsibilities and duties centralized instead of more evenly distributed?
One way to answer this question is to borrow a concept from economics known as the Pareto Principle. This principle, slightly reworded, states that 80% of the work is done by 20% of the people. This concept plays out in many different fields beyond your question in relation to academics. The talented people tend to do produce way more than the average and not so talented.This gives the appearance of centralization when it is really just the 20% producing 80% of the results