Businesses regularly and routinely run a number of software applications as part of the business management workflow process. There are for example decision support applications which are  run in-house.  A typical business would not wish that such application's data ever be breached or leaked to a competitor. Such applications will run in the private cloud. However, unless the company is a subsidiary created to serve the mother company only, typical business considerations dictate the need for a secure external interface in order to reach the intended customers.