The USPS is actually one of the best-run government operations. Not exactly a ringing endorsement for the government doing anything right is it.
When you ask any form of government to do a job you should be prepared for failure.
The only reason that the USPS does as well as they do (again not very good) is that they have some competition. 99% of other government operations have zero competition and only exist because we are forced to use them. They would die if exposed to competition.