The simple answer is “experience” and “efficiency.” A mid-size to large company may have operations and accounting teams that could take on those roles, but the bulk of their responsibilities lies within running the company and the numbers. They most likely do not have time to be market or industry experts and gain valuable industry relationships. Take Coca-Cola for example. They are focused on when they know best, the beverage business. Although Coca-Cola may have the resources to start or acquire an aluminum or plastics company to manufacture the packaging, they choose to purchase packaging from suppliers to focus on what they do best. This saves them time and money.