[trelliscoded]

Replicating a huge database between AZs, let alone regions, can be an enormously expensive ongoing operational cost. Not everyone can afford it.

[poxrud]

Assuming you're using RDS then multi-AZ deployment is just a simple configuration option. If you're using Aurora then it is handled automatically and is even less expensive.

[madisp]

don't all the multi-AZ deployments imply at least 1 standby replica in a different AZ?

[dabeeeenster]

Aurora can replicate the data but doesn't have to keep a hot standby AFAIUI. You can then start a new instance in a different az but the process is semi manual.

[poxrud]

Yes, my point was that it is not complex to setup and maintain, but it is not free.