Sure, from the perspective of availability, it makes sense to keep this around. The US military has redundancies in place to handle many kinds of adverse scenarios, which comes at a price, but is justifiable. The point I'm trying to make is that if availability is the _only_ value, it becomes hard to justify that if you're a scrappy for-profit corp looking at your bottom line.
If instead of availability being the only value, there would be a more value provided from actually using such resources, more folks would adopt cross-AZ architectures which would be a win-win for both the customer (get HA for lower or no cost and go down less often and succeed in the market) and thus the cloud provider (keep raking in the steady cloud revenue as the customer grows).
If instead of availability being the only value, there would be a more value provided from actually using such resources, more folks would adopt cross-AZ architectures which would be a win-win for both the customer (get HA for lower or no cost and go down less often and succeed in the market) and thus the cloud provider (keep raking in the steady cloud revenue as the customer grows).