For any delivery that would near the blue route in the map below the Nevada location is not out of the way compared to the distance of the normal route of the car carriers. And it's much more secure at the Gigafactory with 24/7 guards in a low population density zone than to put them in major cities all over the US.
Pretty much all of Florida, Georgia, Tennessee, Missouri, and Nebraska are covered well by that route. Carriers can branch off the main route in Nebraska for coverage of most anything east of the Mississippi. Staying North to cover Iowa, Illinois, Indiana, Ohio and the Northeast corridor.
Sure anything going to Arizona, New Mexico, Texas, or Louisiana shouldn't go to the Nevada lot.
But there is room for a lot that would be able to go that way without wasting much time/distance.
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