My engineers are all React and CSS web developers. They don't know anything about multi tenant data resiliency. But they can make a real pretty "system down" page.
Without data it doesn't even cost significantly more than running in a single region nowadays, if you are willing to go serverless. As serverless stuff (FaaS, ...) is pay for what you use and the provider handles the scaling automatically behind the curtain you can easily deploy to multiple regions without much additional cost.
With data you have of course the cost of storing the data multiple times in the different regions (or to come up with some kind of sharding) and solving the consistency challenges that come with that, but at least services like DynamoDB and S3 offer cross-region replication out of the box nowadays and you don't have to provision any capacity like you used to (thanks to DynamoDB AutoScaling and so on).
Once you have your application running in multiple regions you can direct users to the closest one, so they enjoy lower latencies.
I believe for a lot of applications running cross-region just makes a lot of sense as it offers various benefits.
Always CYA guys... you will pay for this if you dont.
An outage like this happens how often?
Edit: Looks like this is affecting a single AZ... so bit different situation, but I would agree if you're not capable of surviving a single AZ outage in 2019 then your engineering team should be replaced.