[pjc50]

The field studying this is "organizational cybernetics". Fallen out of fashion recently, but still important.

As to why a company is a single large integrated organization rather than a cloud of independent organizations or individuals bound by contracts: see Coase Theory Of The Firm. It's to do with information flow.

The critical difference between corporate central planning and Communist central planning is that corporate still has prices, mostly from outside the organization, which also represent a flow of information. But that 30% of intra-corporate trade often does not have anything close to a real price on it, instead it will have a number chosen for tax optimization purposes. See Apple Ireland, for example.