The reason I have so many books waiting to be read on my Kindle is because once I read and fall in love with a book by a new-to-me author, I proceed to buy all of her backlist and just glom onto it right then, even if I already have 100+ other books already loaded onto the Kindle.
You may say, "Well, what difference does it make if you read the book, as long as you bought it in the first place?" Sure, that works for this one sale, but it's not forward-thinking at all. You want your readers to buy all your books, not just buy one and never read it. And if you don't give me a reason to want to read your book (ie, remind me what it's about the next time I'm scrolling through my queue looking for a book to read), then I just won't. Which means that sure, you got yout $2 royalty on that sale (assuming I bought the book instead of merely downloaded a sample), but you lost out on the royalties for all the other books.