I mostly speak from experience designing, implementing and operating a distributed database/storage system and traditional storages, databases before that.
And you've never seen the storage stack give back bad data?
You seem to be saying "checksums don't matter because there may be nothing we can do about about the corrupted data". So we should just blindly accept all the bits from the lower levels of the stack? We should do nothing to verify that those levels of the stack are working correctly?
You've mentioned application-level checksumming: yes, that would be good. But until every single dev adds code to checksum (and correct?) their data structures and file formats, having more checksums allows for beter information about when corruption occurs IMHO.
My point is checksumming is not a solution for data corruption, never was, never will be. It's only a tiny part of more complex algorithms and systems that detect and fix corrupted data automatically, never something usable on its own.
