I would also argue many aren't even using multiple availability zones, as evidenced by the wide array of problems on the internet when a single AZ goes down.

I think you're vastly over-estimating how most companies are using AWS, and are substituting your own requirements for theirs.

Which is very common in tech. It's part of why people shit on cloud, microservices, and other techniques large mega-corps use on HN. People write posts with lots of assumptions and few details, then people that don't know any better just carbon copy it because hey its what Google does. Meanwhile their lambda microservice system serving a blazing 60 requests per minute has more downtime than if I just hosted it on my laptop with my dialup internet connection.