Each new link in the chain adds costs and transactions, each link eliminated shifts responsiblity and costs. These functions are absolutes - the raw materials have to be transported to manufacturing. Manufacturing has to do something. The final stuff has to get to the customer. Now you can argue some agricultural products don't have manufacturing, but processing may be involved - but we'd be splitting hairs.
Specialization is the key to our economic vitality.
The creation of surpluses allowed civilization to trade and lifted us from a hunting and gathering to an agrarian economy. Specialization allowed for mass production. Specialization also drives costs out of the system. Let's just say a company chooses to move its own raw materials - it needs transportation, drivers, docks, handlers, claims and customs agents, etc. All of these costs and inherent direct and indirect labor costs are absorbed by a manufacturer who is in the business of making pipes, not transportation.