Comment by colanderman

Accidental drive pulls happen -- think JBODs and RAID. Ideally, if an operator pulls the wrong drive, and then shoves it back in in a short amount of time, you want to be able to recover from that without a full RAID rebuild. You can't do that correctly if the RAID's bookkeeping structures (e.g. write-intent bitmap) are not consistent with the rest of the data on the drive. (To be fair, in practice, an error arising in this case would likely be caught by RAID parity.)

Not saying UPS-based integrity solutions don't make sense, you are right it's a tradeoff. The issue to me is more device vendors misstating their devices' capabilities.