[ironcan]

This is the important question, why is this feature even on by default? Why is it an option to NOT have that feature?

[giardini]

For the same reason most, if not all, copiers and printers embed hidden markings into output - so 3-letter agencies and law enforcement can track documents:

https://www.google.com/search?q=hidden+markings+in+printed+p...

[hnaccy]

I have to agree. Storing thousands of old documents does not seem like an accident.

[pwg]

The code running the copier likely did an unlink(filename) when done with the job. And once deleted, it looked like it was gone from the point of view of looking at a directory listing of the drive.

Of course the programmer writing the code did not consider all those "undelete" utilities that exist to "undo an unlink(filename) operation" and how they might just be used to recover the files.