> USPS benefited from national mail logistics only being available to government level endeavors.
What Kool-Aid are you drinking? The Post Office didn't benefit from anything, it was mandated because no such service yet existed.
Prior to the Office of the Postmaster General being established, postal service was disjointed and limited at best in the colonies. In the 1600s you had 2 routes in the colonies, Boston to England and Boston to New York City. It was prohibitively expensive and limited largely to business and government communications. In the 1700s the Imperial Postal Service was extended to the colonies with fixed rates and taxes included, and it was incredibly unreliable.
The Post Office was born out of frustration, one of the founding fathers ran a news paper and the Imperial Post couldn't even deliver papers reliably. The Post Office was mandated by the founding fathers under the principle that everyone has the right to secure, efficient, reliable, and affordable mail service.
With the advent of the Interstate Highway System and many other technological advances over the prevailing 200 years, the Post Office was actually able to reduce costs and turn a profit.
During the civil rights movements of the 50s and 60s, the postal workers began protesting and striking because work conditions and compensation. They eventually won the right to unionized. In response to unionization the Postal Reorganization Act (PRA) of 1970 abolished the Post Office Department and turned the Post Office into an independent agency that was excluded from the US Budget.
One could argue that the PRA was the start of union busting tactics employed by the conservative government in power to bankrupt the post office. It doesn't help that every conservative government since then has enacted some sort of constraint upon the USPS that isn't mandated on private services. The most recent being the Postal Accountability and Enhancement Act of 2006 which required the USPS to switch from a Pay-As-You-Go to a Pre-Funded model for it's retirement plans. That's akin to your mortgage company calling you up and saying you'll need to pay off 100% of your principal next year.