Some years ago the post office went to a semi-hub system... they have multiple sort centers around the country and all mail goes through those sort centers... I live about 70 or 80 miles from Chattanooga which is (I think) the sort center for this part of Tennessee.... we mailed a Christmas card to our neightbor that lives behind and above us... I go up his driveway to get my truck near my shop... the card went to Chattanooga and back for delivery.... everybody in Tellico Plains knows my neighbor... he is a big member of the local chamber of commerce, heads up the Christmas parade, 4th of July parade, the wagon train over the Cherohala Skyway and is a proctor at all local elections. A good number of locals have bought cars from him when he ran the local auto parts store and had a car sales lot in the parking lot.... you would think the mail carrier that goes from my mail box to his on the next stop .... ??
Same is true if you use Fedex -- every package goes to Memphis to be sorted and returned.... when I was still working, one of my tasks was to negotiate letters of credit for my customers... usually issued by a down town Houston bank.... Fedex picked up the documents at my office at the junction of the I10 and I610 enterchange, about 12 miles from downtown Houston... Documents worth any where from 1/2 to $1M plus flew to Memphis and back to be delivered 12 miles away.... When I worked in San Francisco, did similar work and had similar results.... documents flew from SFO to MEM, then back to SFO for delivery.
UPS uses a similar system, but I don't remember where their hub is located.