I absolutely have a UPS in my basement. Considering how little runs on it, it's pretty cheap to get a long runtime out of it too.
A lot of things I see with millions of concurrent users aren't actually monoliths: Sure, Facebook needs to handle that. But most cloud apps would better be run where each tenant/business/team operates an Intel NUC in their basement, instead of the developer using the cloud as a way to force rent-seeking behavior.