My house is pretty rural and both FedEx and UPS deliver without issue. Both drivers are in company trucks and have been very friendly. USPS on the other hand uses what they call a "Highway" delivery (independent contractor) and will only deliver to a mailbox located on a paved road.
Even though I have an oversize mailbox, Billy, the operator, usually will just drop a delivery notice even if it is a small package. He drives a Jeep and probably doesn't want to carry packages because they take up too much room. That means a 20 mile trip to town to pick up.
I complain at the PO and service will improve for a while, but the agents at the PO are some of the nastiest people you would ever want to meet.