It's a game theory thing. If everyone stays single AZ, everyone goes down at the same time so nobody gets blamed. Somehow the blame falls on AWS instead!
That’s a feature, not a bug. If we all had the same number one ; then things would not be loaded anything close to evenly. There is some command to find out what the unique ID number is for your particular zones with your naming.
Clarification: 1/3 of sites will go down (those using the AZ that went offline), but my point is the same. Most companies aren't using multiple AZs, let alone multiple regions.
AWS AZs don't even have consistent naming across AWS accounts.