I mentioned to my mother that the Post Office is now talking seriously about stopping Saturday delivery. She said, "That would be bad, but not nearly as bad as we thought it was when they stopped delivering twice a day."
Apparently twice-a-day delivery stopped during World War II as an economy measure and was permanently discontinued shortly thereafter.
When the service existed, it was possible to send a written message to someone in the same city and get an answer the same day. We take that for granted now with email, but for years after twice-a-day delivery was ended, round-trip communication seemed to take longer than it should.