Postal Service is less necessary than it once was, but it's still a vital service, and a good one, especially in areas where the commercial shippers are not set up to handle. I asked a business in California to ship a vital repair part for my boat, which was in Sitka, Alaska. I asked that it be sent by the Post Office. He said they always use XX (I can't remember if it was Fed Ex or UPS), and never had a problem.
A month later, I called the shipping company to find out where my part was, and they responded that it had been delivered. After several more attempts to locate the part, and the same default response each time, the package was located in some warehouse in Juneau, where they apparently didn't know how to get the thing to Sitka. It took two months, and most of the time it was effectively "lost." Packages from the lower US to Alaska take about two days using the Post Office, because most of it is done by air. The Post Office knows how to get to where you are, even if it's in an isolated community.