Here in Canada, we only receive mail on weekdays. It works just fine because the majority of letters in our mailbox are not extremely time-sensitive - the occasional municipal bill, magazines, and periodic greeting cards from around the world. They could reduce letter delivery to M/W/F without really causing any issues. Daily parcel delivery makes sense because they're larger dollar transactions and whenever a parcel is on the way, someone is waiting for it. I cringe every time someone suggests getting rid of the post office and relying on FedEx and UPS instead, because they tend to be far more expensive in Canada. As an example, UPS will charge a brokerage fee for surface packages coming from the USA that easily hits $25. Sending a 2 lb package to the USA by UPS Express (even 3-day) costs about $60. Canada Post runs about 25% of that.
Back to the USA, there are already some interesting private/public delivery programs that promise to keep service costs low, too. As an example, Smartpost is an economical FedEx service that uses the USPS to deliver the last mile. Expect more of this stuff in the future.
To the systems programmer, users and applications serve only to provide a test load.