Easy, it’s the difference between a service and a business. War is a business, run by profiteers who charge $1000 to produce and deliver a hammer or a toilet seat, whereas historically the postal service was a pure need met by the government and subsidized by the people, but seen previously as such a critical means of transferring critical information, news, it was necessary to prop up the entire economic system by transferring contracts, documents for business, government, personal dealings, so it had to function and the cost was not a consideration, gouging wasn’t dreams of, and it piggybacked on all the major and newest modes of transportation. Today greed and political malfeasance has intentionally spread the idea that the postal service should be profitable, for some to kill it off or raise prices to enrich their own investments in competition, for some to damage voting by mail, for some to further sow distrust in reliable government services to convince the masses that the government is entirely incompetence and untrustworthy to run such programs to further privatize various industries.

It was cheap because capitalists relied on it to enrich themselves. Now they can do their business in other ways cheaper, so they can do what they always do - raise prices, enshittify it, strip the parts and sell them off once people lose faith in it, then use their corporate monopolies that provide the same services to gouge the populace that previously paid pennies for the same services.