What's the point of cloud if we have to manage robustness of their own infrastructure. I can understand if that's due to natural disasters and earthquakes, but the idea should be that a single AZ should never go down barring extraordinary circumstances. AWS should be auto-balancing, handling downtimes of a single AZ without the customer ever noticing it.

It might not be a good analogy, but if a single Cloudflare edge datacenter goes down, it will automatically route traffic through others. Transparent and painless to the customer. I understand AWS is huge, and different services have different redundancy mechanisms, but just conceptually it feels like they're in a conflict of interest to increase robustness of their data centers - "We told you to have multi-AZ deployment, not our fault".

Another way to put this is make sure as an AWS customer, to 3x multiply all costs + management of multi-AZ deployment into your total costs.