How often do the AZs matter? - I feel like there's a major global outage on every cloud provider of choice, at least every other year, yet I don't remember any

How often do the AZs matter? - I feel like there's a major global outage on every cloud provider of choice, at least every other year, yet I don't remember any outage where only a single AZ went down (I'm on AWS). Fighting said outages is often made harder is that the providers themselves just don't admit to anything being wrong, everything's green on the dashboard yet 4 out of 5 requests are timing out.