> If you believe in the classic explanations of the theory of the firm, "companies" exist so they can be effectively communist on the inside in an attempt to lower transaction costs. If you have teams competing against each other directly for resources, time-to-market, etc. you don't really have a reason to be a single company anymore.

Sure you do. It allows someone at the top to flip the switch between market and central command. Ideal firm size and vertical consolidation varies between industries, and plausibly varies in different environments, different times, etc.