I work in the healthcare industry and there's a big push from AWS into offering HIPAA compliant services for things like patient records. It's becoming much more common to tie in third party services into electronic healthcare software. Obviously no mission critical system should have a single point of failure and doctor's offices should have fallback plans for handling service outages, but most care providers don't have staff onsite with the technical expertise to understand the extent of the coupling. I'm just closely watching this space and found that tweet interesting in relation to the parent comment's remark about realizing the scope of this S3 outage. There's no blame unique to AWS here, but it is becoming an increasingly important piece of plumbing in the industry.

Whatever software that doctor is using should have been built with offline capability (local storage, syncs to servers when network connectivity is restored).