Look, it's the culture. Postal people have a natural antipathy toward loose dogs, or angry dogs, or snarling dogs. Some people like to walk up and huggybuggy with strange loose animals of all kinds, and stick their hands into the mouths of angry dogs, or even set their children on top of snarling dogs to take a ride.
No, the Postal Service didn't put the box on your house. The owner did. Time for you to move to street service or post office box, or maybe even GENERAL DELIVERY.
If door delivery causes you offense, take action to stop it!
Nope, it has to do with the people selection process of the USPS.
The USPS is there to provide a service. They have handled it well in the past.
That they have a problem now if their fault, not mine.