Shipping through the USPS

This "partner" shipping, doesn't make any sense to me. Leaves the vendor in Texas, by UPS. They deliver it to the post office, about 25 miles from me. Then post office delivers it to my mail box, in Florida. Takes 5 days. If an item ships UPS from Texas to me, it takes 3-4 days. If USPS it takes 2-3 days. Go figure.