> They don't make the computers, fiber optics, switches, exchanges, or software that their web site requires to run.

Because they don't need to. The quality of their network setup has no, utterly no, relationship to the quality of the final product - the machines and materials however do have such a relationship and therefore it's done in-house.

Additionally this vertical integration removes the incentive for a supplier to cut corners somewhere for more profit - which is something that Tesla and SpaceX also have discovered and apply it wherever they can.