When I was younger and living in Missouri, we had both a morning and afternoon delivery by the Post Office. I'm not sure when that changed but now it's once a day and it seems to be whenever the carrier gets around to it; sometime between 10 a.m. and 5:30 p.m.

In the 1940's and 50's the carrier walked and carried the mail in a leather pouch. Now he drives a vehicle and puts the mail in a neighborhood arrangement of locked boxes. His vehicle is usually piled high with boxes so walking would not be an option anyway.

In the old days, both Sears Roebuck and Montgomery Ward had catalog stores in the smaller towns and also printed thick catalogs of their merchandise available by mail-order. It's not just the availability of electronic ordering and the internet that is creating all those boxes for USPS to deliver!