Understood, was only making the point that blanket statements by anyone (there have been several in here and the other BB MB thread) that anyone can just go to USPS and grab one and it'll work, is untrue. Like the two post offices I went to, many are expires, and exempt online purchases.
It may be in areas where people are a little behind in tech. I live in the tech capital of the world, SF... here NOBODY goes into the post office to change their address, this isn't 1965... people go to usps.com to do it. So it's likely they go through the packets a lot slower than middle america or places where they're less apt go go online, and more likely to stand inline to buy stamps or change their address.