Why would booksellers buy a title without knowing anything about it?

Slate.com wonders Why would booksellers buy a title without knowing anything about it?
Because “blind” books are almost always big sellers. Publishers rarely try to sell a book blind, and when they do, it comes with a promise that the title will make a big splash. Sales reps might keep the details of a blockbuster hidden to make sure no juicy bits are leaked to the press ahead of publication. Under normal circumstances, the reps would provide book buyers with lots of detail on the titles they purchase, occasionally sending along excerpts. So, if they try to sell something blind, a buyer can be pretty sure that the publishing house is holding an ace.