A mineral company, such as Alcoa, owns the equipment to explore and extract bauxite, then to smelt, refine, fabricate, ship and market the aluminum. This total control of production provides protection against new competitors entering the aluminum field. It also allows Alcoa to avoid national taxation by setting its own price at each step of production. With vertical integration, a corporation is also insured against a fall in the world price of the mineral or material, since any losses can be made up at a later stage of production. Most corporations prefer to be as 'capital intensive' as possible.
Equipment is much more reliable than human beings.
Since the costs of an individual's labor is an ongoing expense that rises with inflation, it does not compare well with the cost of a machine that is purchased only once. In terms of global resources, it may be more advantageous to use human labor power to produce goods. To the large transnational labor is a headache it doesn't need. A machine that can do the work of a hundred men is more reliable and adds to the corporations overall worth. Human labor always represents a possibility of unionizing, absenteeism, strikes and pay increases.