USPS* is acting like a retailer and following patterns of distribution and logistics that have been in place for centuries. Not everything is about software..
If someone is more familiar with a CDN that the traditional retail logistics and distributions infrastructure, then it would probably be more helpful of them to think of the situation using that analogy.
USPS is acting both like a retailer, and as a sort of an analogue to a CDN. Both can be helpful models in understanding how this works.