I'll come out and say it.
UPS, et.al could do it better, cheaper and turn a profit.
But, they don't. So, why don't they?
They are prohibited by law from carrying first class mail equivalents. Seems you would know that be so up to date on legislation and all.
So you are saying the PO's monopoly - and their ability to overpay desk clerks - must be protected by law at the expense of the American consumer?