I agree with you, but my services are actually in Canada (Central). There's only one region in Canada, so I don't really have an alternative. AWS justifies it by saying there are three AZs (distinct data centres) within Canada (Central), but I get scared when I see these region-wide issues. If the AZs were really distinct, you wouldn't really have region-wide issues.
Take DynamoDB as an example. The AWS managed service takes care of replicating everything to multiple AZs for you, that's great! You're very unlikely to lose your data. But, the DynamoDB team is running a mostly-regional service. If they push bad code or fall over it's likely going to be a regional issue. Probably only the storage nodes are truly zonal.
If you wanted to deploy something similar, like Cassandra across AZs, or even regions you're welcome to do that. But now you're on the hook for the availability of the system. Are you going to get higher availability running your own Cassandra implementation than the DynamoDB team? Maybe. DynamoDB had a pretty big outage in 2015 I think. But that's a lot more work than just using DynamoDB IMO.
> But, the DynamoDB team is running a mostly-regional service.
this is both more and less true than you might think. for most regional endpoints teams leverage load balancers that are scoped zonally, such that ip0 will point at instances in zone a, ip1 will point at instances in zone b, and so on. Similarly, teams who operate "regional" endpoints will generally deploy "zonal" environments, such that in the event of a bad code deploy they can fail away that zone for customers.
that being said, these mitigations still don't stop regional poison pills or otherwise from infecting other AZs unless the service is architected to zonally internally.
Yeah, teams go to a lot of effort to have zonal environments/fleets/deployments... but there are still many, many regional failure modes. For example, even in a foundational service like EC2 most of their APIs touch regional databases.
