You may want to be able to run highly resilient databases even on non-error-detecting hardware. (Most consumer disks, and even a lot of enterprise disks, don't reliably detect/report disk corruption)
You might also be building a distributed system, where blocks are spread across multiple disks. In that case, an "error" you're trying to correct might be the loss of a disk or server in the distributed system; there is no one single disk or OS responsible for all the relevant blocks in that case.
But, both of these are assuming you're building some kind of data-store, which is not a typical user application. Writing robust data-stores is hard for many reasons, error correcting is just one of them.
Comments
You may want to be able to run highly resilient databases even on non-error-detecting hardware. (Most consumer disks, and even a lot of enterprise disks, don't reliably detect/report disk corruption)
You might also be building a distributed system, where blocks are spread across multiple disks. In that case, an "error" you're trying to correct might be the loss of a disk or server in the distributed system; there is no one single disk or OS responsible for all the relevant blocks in that case.
But, both of these are assuming you're building some kind of data-store, which is not a typical user application. Writing robust data-stores is hard for many reasons, error correcting is just one of them.