It is true that a company can be broken up into different pieces or verticals for different reasons, but the key is that they do not act like an internal market where profit is extracted from each interaction with one another. For the most part they are allocated a set of resources and charged with delivering whatever they are responsible for, and then every year they are re-budgeted to achieve the same results or better, ideally at the same cost or less. Savings are transferred out and eventually to the shareholders.

So, what I am saying is that instead of having lots of different companies extracting profit from one another at each part in the system, creating inefficiencies, a large company can basically dictate down what everything costs and wherever excess value can be extracted, it is done more efficiently, captured more completely and transferred upwards towards a single set of shareholders.

Basically a corporation is a perfect command economy