It's the other way around: bulk mail is incredibly cheap to sort, route, and transport, and it's that which subsidizes your hand-addressed letters. The USPS li

It's the other way around: bulk mail is incredibly cheap to sort, route, and transport, and it's that which subsidizes your hand-addressed letters. The USPS literally has a service "deliver this flyer to every residential mailbox in this ZIP". It's cheaper per-item than a letter, yes, but the margins on "stuff a bunch of identical objects into N boxes" are much higher than "figure out which of N boxes this 1 unique mailpiece goes to".