If you want a government program to deliver mail to obscure locations at a loss, create a program to do that. There's no reason for the government to assume responsibility for delivering all mail, and especially no reason for it to make it illegal for others to deliver mail!
And especially, especially no reason to protect the program from being cut as mail slowly becomes obsolete.
Must government insist on solving 100% of the problem when it doesn't trust the free market to handle that 0.5% case?