This is because the idea of economies of scale is easy for buyers to understand and impossible for them to duplicate. Vendors push the idea of scale because it overcomes a buyer's resistance since they could never generate the magnitude of cost savings internally. Where economies of scale do exist, they are very powerful and extremely beneficial. Some areas of outsourcing form a natural fit. Net hosting is another.
Network management is a third example.
ASPs leverage a single application platform over their entire customer base. Shared services centers and call centers allow BPO providers to pass along significant savings to all their users. BPO providers also generate cost savings through their combined purchasing power. Often, scale plays multiple roles in a specific outsourcing relationship. For example, a single buyer can enjoy savings by outsourcing claims processing and using the vendor's imaging center, data center and call center.