Actually, it was 10 miles round trip so 5 miles to the PO. No, it's not a long damn way. Five miles to country folk is nothing. It's considered "down the road", by the neighbors', or across the creek. Out of milk for breakfast would mean a 40 mile round trip for me (not that I'd drive in for milk but hubby would) which is about average for country folk here.
Then you must live in an extreme outlier of what is considered a rural area or out West . It would be a rare area indeed East of the Mississippi to draw a 15 mile radius from a point and not encircle a corner store selling basic groceries.
Even when I used to do hiking an camping all through Wyoming and I felt like I was really out there, when you pull out a map, you see civilization is just 20 miles away. It may not be much - just a bar and a gas station. But the beer truck, Frito Lay and Pepsi distributor make it there every week.
Maybe we should have Anheuser Busch haul the mail. No matter how far you go into towns that time forgot, their product makes it to the shelves.