It's not unheard of near me in a rural area to have a diesel generator in your garage as the electricity's unreliable just enough of the time, and especially given working from home is common nowadays losing electricity for 6h now and again isn't acceptable. That's not running your own generator for electricity as in your analogy, that's having a reasonable backup for short term redundancy. I think it's reasonable for companies to act similarly, rely on cloud but have a backup that provides at least degraded functionality as opposed to none.