UPS ships to Post Office ?????

At work, I get parts delivered from the manufacturer in Atlanta. They use FedEx. Sometimes the parts are delivered to the FedEx depot in Clive, IA, where they are then delivered to my shop via FedEx truck. Other times they are delivered to the depot in Kansas City, where they take them to the USPS. They are then delivered to me by the Postal Service. All I can say is ??????