As it turns out, rational people actually want to cut costs. This is true even down to the individual level. And time is money, so nobody wants to spend the effort to be decentralized when a centralized system exists that takes less money. Rational choices are what bring centralized systems into existence.

Buying a car from a dealership instead of mining metal from the ground and building it from scratch is a cost cutting measure.

Buying my food from a market instead of foraging for it is a cost cutting measure.