I am an admitted layman in the field of postal engineering, but I would guess that the issue here is that there is twice as much sorting to be done - the number of recipients hasn't doubled nor has the physical area of the delivery route doubled.
Since NONE of the people getting delivery paid for it
None of them are taxpayers at all?
Not a single one?
I'd suggest that after a letter carrier gets shot on his route that all the people on that route, and in nearby areas, have delivery service withdrawn until the problem can be sorted out.
I'm not sure why a lunatic's neighbors should be punished for the lunatic's actions.
How much tax money do you think the Postal Service gets - more or less than UPS or FedEx?
As far as "sorting" is concerned, it is necessary for carriers to "sort" mail into their delivery route sequence, or where the mail is already pre-sorted, to insert it into the correct sequence so it is available for delivery in a workable order. They also co-sequence mail of different sizes. Recall from your cubscout tour of a major mail processing center that mail is worked as different types according to size, e.g. letters, flats, SPRs, parcels and outsides.
The consequence is that carriers have what is called OFFICE TIME, and that's where they assemble the mail into cohesive segments for delivery. They also have STREET TIME. Obviously Office Time is going to vary with the mail volume, but Street Time also varies since the carriers need to "finger the mail" to take care of tiny errors made earlier (by them, or by automated mail distribution systems).
We are getting into the Christmas Season so mail volumes ~ particularly advertising ~ is up, and Veterans Day was a regular business day although not a workday for USPS.
In effect this doubled the normal expected mail volume.
This generated additional carrier Office Time and Street Time.
Sometimes the wrong dog is blamed, or the people in the community seek to protect the dog.
Same with lunatics.