Given the scratch-ability, the suggestion that these things are practical for robust archiving is laughable.

But if they're handled carefully I can imagine them being useful for smuggling data across borders by hand or by mail. Which makes them potentially useful for money laundering, one time pads, and such - at least until customs services catch on to what they are.

There are better and less showy ways to do all of the above, but presumably you can print a cover photo or message with some embedded steganography, and the data content won't be visible to casual inspection - an application of sorts, I guess.