Why will my packages sit in Phoenix for 6 days before delivery?

basketballJones thought this was worth mentioning said

Shipped 4/07/17. Arrived in Phoenix 4/08/17 from CARROLLTON, TX US (814 mile trip). They could have just dropped them off at the Tucson FEDEX hub on their way North to Phoenix (118 miles north). Now I have to wait nearly a week (due 4/14/17) for my packages to make their 2 hour trip back south to Tucson!!!