You're right that important data needs to be backed up, but I disagree that it is the app builder's responsibility to do that. It is the end-user's responsibility to think about backups, to choose where to backup and how often. From the app developer's perspective, it is commendable that, in this day and age, they allowed users to retain control of their own data, instead of automatically uploading the user's data to the developer's server.

Local storage and/or SQL DB were touted as features for exactly this use case. That Google did not consider their persistence as that important for the release is perhaps not surprising for a company used to storing all your data in their cloud (not claiming they did so knowingly, just that it's probably in their culture, just as in your comments above).