You don't NEED to be able to download books directly from Amazon, upon purchase. It takes all of ten, maybe fifteen seconds to simply download said purchases onto your computer, and then importing them onto your Kindle from there. The device (and its contents) is then wholly under your control, and not Amazon's.
I would dearly like to know how to do that, since I have been trying for years to download the Kindle books I have on Amazon to a local (linux OS) computer and the site will not allow it, stating that they can not identify a Kindle device to download to.
Finally gave it up as a Lost Cause. :(
As far as that feature is concerned, Amazon is as helpful as a Bangladesh Computer Repair and Chicken Currie Recipe website.