I had a realization that the very existence of private domestic shippers in countries indicates a failure of their government to provide universal infrastructure needed by all citizens.
There may be specialized needs like same-day couriers, special handling requirements and other edge cases, but those should be small specialty houses, not international mega-corps.
The required obligations of the USPS do hamstring them competitively in some areas, that is true. That said, I don’t believe their charter requires them to permit repackaging and reselling their service.
Since this is a tax-subsidized public amenity, it strikes me as an abuse of the commons to allow a shipping company to ship things on someone else’s behalf using the USPS. It seems directly analogous to digging up the flowers in the park and selling them.