Comment by nrmitchi

There is also the consideration that this isn't even an argument of "other things are down too!" or "outsourcing blame" as much as, depending on what your service is of course, you are unlikely to be operating in a bubble. You likely have some form of external dependencies, or you are an external dependency, or have correlated/cross-dependency usage with another service.

Guaranteeing isolation between all of these different moving parts is very difficult. Even if you're not directly affected by a large cloud outage, it's becoming less-and-less common that you, or your customers, are truely isolated.

As well, if your AWS-hosted service mostly exists to service AWS-hosted customers, and AWS is down, it doesn't matter if you are down. None of your customers are operational anyways. Is this a 100% acceptable solution? Of course not. But for 95% of services/SaaS out there, it really doesn't matter.