I am not sure that the fingerprints won’t be gathered passively, and perhaps without the customer’s knowledge. If not yet, then very soon! Already many things and IDs require fingerprints to be taken. If the USPS is getting in on this, that means that somewhere the government has a database of citizen’s fingerprints, and is wanting to add to it to fill in the gaps of people who haven’t yet submitted theirs. People who haven’t done so already are probably going to use the post office and so will get their prints nabbed there.
Think: an automatic stamp dispenser or postage calculator with a touchscreen. Use it once, provide your name and phone number or email and your prints are on file.
Then with a complete fingerprint database, many crimes could be simply solved by checking all prints at the crime scene against the database.
FREEDOM! to self-screw. What is next - voluntary submission of DNA samples?