I have a DXG, it doesn't have WiFi... Why should I have to pay for wireless delivery?
You can mail it to
xxxx@free.kindle.com and download (upload?) it from your PC to your Kindle, as you say. That's a fair equivalent, it seems to me. (I have a K2.)
There is after all a cost for the wireless. Amz doesn't want you running up charges wholesale, for example by blasting books to a hundred Kindle-owning students in a literature class.