I Don't Get Book Trailers!

Call me old-fashioned or old-school but I don't get book trailers. I fail to see how a book trailer can do a better job than a well-written blurb to excite a potential reader. I'm not against using a different medium to promote a book however a trailer is so limiting with regards to the reader's imagination. It's just like a film that can rarely be anything other than a pale interpretation of a book.

I understand it is a marketing tool and it is important to reach a wider audience when promoting. But someone who picks trailer over blurb, forgive me if I sin here, is probably not a potential reader to start with. He/she would wait for the film to come out. All right. I'm probably being a little bit too unfair. All joking aside, is there science behind book trailers? Is there really potential readers who wouldn't be reached if we didn't have book trailers? Has there been a book trailer that makes justice to its book or that makes a better job than the blurb?

Do you care about book trailers? Have you ever bought a book thanks to its trailer?