But that would require companies to actually spend time and money testing and working with either a cross-provider multi-master-type system (with all the associ

But that would require companies to actually spend time and money testing and working with either a cross-provider multi-master-type system (with all the associated consistency headaches) or regularly test a functioning disaster-recovery/fallback system. The time spent on that (let alone cost, for companies with large amounts of data) far outweighs the cost when a single region has an issue of today's scope. And you said it yourself, it's a 'small benefit'. Small benefits sound like exactly the things not worth spending time or money on. For as much as many companies have had issues today, the daily reality is that these same companies haven't been having issues all the rest of the time (or this wouldn't have felt so shocking) and are likely to be okay with an outage of this scope (plus, everyone's too busy making noise about the issues to be working normally).