Companies and Enterprises have unique needs in maintaining legacy applications and control in their network. Keeping things completely on-site poses a huge problem in case of a rack server going down or a slowdown in the pipeline somewhere else. This can put the brakes on the entire network with a complete shutdown until the fix is made.
Using the Cloud can ensure redundancy in applications and data, even when a server goes down. Using virtual applications and virtual desktop services ups the Cloud ante even more for total integration with your on-premises setup.