It is my understanding that one can pay extra for uninterruptible power supply,such as hospitals, police stations, communication centers, etc. Likewise consumers with special health needs that require continuous production of oxygen or some other service also may get special treatment. The deregulation of the industry also brought with it various fine print excusions and waivers of liability from some providers, if you selected such providers. I do not think the special treatment is due to a nefarious cabal deep in the heart of the ISO, it is just the way we let it evolve.
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick