Honestly mainframes sound like what on-premise aims for. You get uptime and proactive maintenance and stuff just runs. Yet the machine is on your premise and the data belongs to you.
The magic were the old minicomputers.
My wife ran a billing system that was a Motorola based AS/400. It was purchased in 1989/90. An ibm CE would drop by and swap parts every now and again when the computer phoned home.
They retired it in 2013, when a key part for the printer was no longer available.