The natural cycle in IT is to move from decentralized to centralized services. When networking first appeared, it was implemented at a department level for printer sharing. It was decentralized—resulting in a hodgepodge of networks and protocols. Eventually IT organizations determined that it was much more efficient to centralize this effort and we saw the adoption of large-scale, TCP/IP networks. Today nearly every IT organization has a centralized networking team that manages and deploys IP-based infrastructure.
When SaaS applications such as Salesforce first appeared, they were adopted by sales organizations. As adoption levels grew, enterprises needed centralized data integration, identity and access management, and other functions that are inefficient to deliver at departmental scale. Today Salesforce is typically managed by a centralized IT organization.