they were going to build a sorting facility east of Vegas, but decided it wasn't worth it for one package.

In other words, the route is not determined by the least amount of gas it would take to go from point A to point B. Everything gets routed somewhat out of its way - including telephone calls. Consider our fate in Detroit: a letter sent one mile away to Windsor would have to be routed through Canada Post's main facility in Toronto, adding about 400 miles to the journey.