[usea]

> I suspect the primary issue is that there are simply way less people willing to work as letter carriers.

A family member of mine works for the post office in their city. They don't have trouble hiring for any positions. There is a long waiting list that takes months to get through to be given a chance at the bottom of the totem pole. The various postal unions give the jobs good benefits, pay, hours, etc. Carriers specifically are highly sought-after positions that can set you up for life.

It's not a matter of not being able to find people. it's not willing to hire more people. I would be very surprised if the post office in your town is trying to hire people, but nobody is willing to work. It's a great job, and people line up to work there.