You mean sell a book to a publisher? Not true. I know quite a few authors who recently sold on the strength of the manuscript alone.
I obviously don't mean sell a book to a publisher. I'm talking about books that are already published. I mean sell a book to a bookstore, and then, ultimately, to a reader.
Publishers are not going to waste their money getting good placement at bookstores if they don't expect the book to garner a whole array of prominent reviews.
They have their A releases, their B releases and then all the rest, which get few reviews and are hard to find in bookstores. All of this is determined way before the book even comes out.
Sometimes a C book will get a major review somewhere and then the publishers and bookstores have to scramble. But otherwise, you pretty much know the fate of your book before it even comes out. And it's controlled by the publisher.
Then it's up to you to pack a dozen boxes of your book in your trunk and sell it yourself by the side of the road.