IMO companies that use mainframes are so beholden to their vendor (for maintenance, upgrade, consulting,...) that the trust they must have in their external pro

IMO companies that use mainframes are so beholden to their vendor (for maintenance, upgrade, consulting,...) that the trust they must have in their external provider must be 10x bigger than what you would have if you were relying on a cloud service, particularly from a business continuity angle. Put another way if IBM says they are closing shop in a month time, or they were stop upgrading a particular product line this will royally screw many of their clients who will start scrambling for alternative solutions (although I would imagine they baked in significant notice periods into their contracts). But if you use the cloud and have done it right, it is much easier to migrate from a cloud service to another.