The USPS lost $9B last year. If our government considered The USPS a real public good, they would pick up the bill and give them more budget. Instead, The USPS had to get in bed with Amazon to keep the lights on and start delivering on Sundays.
Certain individuals, such as Susan Collins and Tom Davis, who were the largest names behind the 2006 law to force this on the USPS, were clearly doing it in an attempt to make the USPS fail/become less competitive. PACs affiliated with FedEx, UPS, etc gave more than $192,000 to Collins’s campaign / PAC from 2000 to 2004. FedEx’s PAC has given Collins more donations than any other congressional candidate in that PAC's history.
There is a huge chain of evidence suggesting members of congress don't want the USPS to succeed due to self interest.
Tangent, having lived in 5 states, the USPS workers have always been nice and courteous, even when there are lines out the door during the tax season. And in general, like DMV or other licensing agencies.