They do, that's part of the pay. You could make a (good) argument that they are underpaying their contract drivers, but nontheless -- everytime they pay a cont

They do, that's part of the pay. You could make a (good) argument that they are underpaying their contract drivers, but nontheless -- everytime they pay a contract driver to drop a package off at your house, Amazon is paying for that gas in their pay to the delivery driver. The same is true when they use a commercial delivery service at all -- the cost of fuel tax is bundled into the delivery price. Whether Amazon owns any trucks of their own is immaterial, if they are contracting with Amazom, Amazon is ultimately paying for the fuel (including taxes).