Agreed, but the reason that FedEx does is because of competition.
The USPS used to bundle up mail intended for remote locations in the US and send it all in one big chunk once or twice a week. Now, because there is competition from other companies, they make the run every day.
competition will always lower prices but it would be interesting to see what would happen if there was no usps and no ‘universal service’ provision. I can make at least one prediction: we’d get mail on Sunday