Q: Why private cloud over public cloud?

A: A private cloud is chosen over a public cloud when the cloud data and applications running in the environment must be isolated from other networks. Private clouds are typically run on virtualized infrastructure running in a data center that is owned or controlled by the enterprise IT administrators, whereas public cloud infrastructure is rented and maintained by the hosting vendor. 

When the data and applications as well as all the underlying compute and storage capability is controlled by a single organization for a private cloud, the success and failure for any reason is solely that organization’s responsibility. Public clouds can provide service level agreements (SLAs) to bolster the risk that some organizations might have when the underlying infrastructure is not managed locally.

Related Links:

What is private and public cloud computing?

What is a hybrid cloud service?

How does hybrid cloud work?