Presumably the use case would be you want to transfer secret information from a secure location via an insecure channel to another secure location (e.g. in a diplomatic bag perhaps?).
This is for people who care more about knowing that the data was transferred securely than whether it goes through at all. There would likely be a master (backed up) copy on an internal air-gapped machine.
Or when data is temporarily removed / copied from the highest security locations.
E.g. I was part of maintenance on a defence system once that in itself wasn't very important, but it was kept in an air-gapped concrete bunker with a faraday cage deep inside the office building. Offices outside were used for top secret data during processing, but when people were done working on something, storage would happen in the "bunker".
I'd imagine drives like these would be popular for the offices.
This is for people who care more about knowing that the data was transferred securely than whether it goes through at all. There would likely be a master (backed up) copy on an internal air-gapped machine.