Amazon wants books to be affordable to everyone. Just not with many choices.

From a Vox article on the thin-skinned provider of "content":

3. This policy is part of Amazon’s ongoing, years-long quest to drive down the price of books. If Amazon succeeds, fewer people will be able to make their living as writers. That means fewer and worse books will make it to the marketplace. 

Amazon routinely takes a loss on its book sales, often charging customers less per book than it pays publishers and swallowing the difference. It’s a priority for the company to be your preferred bookseller, even if it has to take a hit; its business model can accommodate the loss, because it generally makes up the extra dollars on the last-minute impulse buys customers toss into their shopping carts. Meanwhile, on the e-book side of things, Amazon’s low prices help drive sales of its Kindle. But that also means it has set certain customer expectations: Many Amazon customers now believe that books should be cheap — cheaper to buy than they are to make. 

It is already punishingly rare for writers to make a living wage from their books. As Amazon drives down the cost of books, it will become ever more rare. That means fewer people will be able to invest the time and effort it takes into becoming a writer, which means a lot of talented writers — especially working-class writers and writers of color — will go unheard. All of which means that you, the reader, will be missing out on some excellent potential books.