I think the postal service is slowing itself down on purpose, in order for us to "see" how much we will miss Saturday deliveries. I believe they are trying to prove a point, that they are so needed six days a week. {insert sarcastic eyeroll here}
On a side note, I know this is the month that many distribution centers are closing, as they consolidate, and reposition team members. (Are they called team members?)
The closing of these centers is adding days to the destination, and will continue in this manner, I believe, until someone balances their budget.