It used to be that most towns had a bookstore, and larger towns or cities had several. Eventually they were displaced by chains: Waldenbooks and B. Dalton, Borders and Barnes & Noble. First the chains chased out the independent bookstores by being able to cut costs and order more efficiently; then the chains ate each other at the same time that Amazon was cutting costs even further. Now there's one limping chain, B&N, and some specialized chains -- mostly religious, secondhand or otherwise discount -- and Amazon.
Efficiency is best served by a single distribution system with maximum economies of scale. That isn't actually a desirable outcome for customers or producers, though.