I've always argued that internet service was the original intent of requiring the USPS as part of the constitution, and that it should in fact offer ISP services. The purpose of the postal clause, per documents at the time, was to establish "a regular system of free and speedy communication" for the "diffusion of Intelligence and useful Information".

To me it's silly or even dishonest to argue that the USPS should be limited to physical mail. There wasn't even electric power distribution at the time, to say the least of internet or radio. The founders had no concept of electric communication. It's exactly what was intended by the postal clause.