From what I understand, the entire reason why we have public goods is because to have it private would cause many people to be left without service.
If it were privatized, the companies would not bother to spend money servicing routes which do not add to their profits, leaving many Americans without mail service.
And honestly, if the private companies had to deliver to every house 6 days a week, they would probably be far less profitable than USPS is.
A public good is something that is nonrivalrous and nonexcludable. Air quality, for instance. If a good is rivalrous or excludable, it isn't a public good. That's the definition of the term.
If it were privatized, the companies would not bother to spend money servicing routes which do not add to their profits, leaving many Americans without mail service.
And honestly, if the private companies had to deliver to every house 6 days a week, they would probably be far less profitable than USPS is.