From the point of view of upper management in a large enterprise, paying a third party with whom they have an SLA and someone to sue for infrastructure which may go down vs. paying their own staff to build and maintain the infrastructure that may go down often either isn't a difference in risk or, actually, the former seems to be better-managed risk. It's the same reason they often prefer to buy support contracts even for OSS rather than supporting it internally. Part of the analysis that probably gets overlooked from the outside is that employees aren't just a predictable cost they also are a risk.