First and foremost, copyright owners have no control over the terms Amazon uses to describe the licensing of an ebook. If they want to use "sell" or "buy," authors/copyright owners cannot stop them even though the correct term is "license."
Authors/copyright owners license their works to publishers who license them to distributors who license them to readers. Then readers are offended because they don't own them when no one else but the author does in this process?
According to "The First Sale Doctrine" which was created by the courts and the US Copyright Office, when you buy a paper book, you own the paper, the ink, and the glue, but you don't own the content. That means you can sell the physical book, but you can't make a copy of the content to sell, nor can you use it for an audiobook, movie, or any other new source of income.
In other words, the only thing you "lose" by buying a digital book is the physical container. In most cases, the lack of that container makes the book contents cheaper.
And, fuzzyfungus, you own the physical CD, not the contents, so the catchphrase is true in a really sloppy way.
Places where you can share ebooks legally do so under an agreement with the publisher or copyright owner.
For more information on "The First Sale Doctrine," I suggest you look at my article on the subject and check out the resources at the bottom for more technical info on the subject.