Why don't advertisements for books and movies have any content?

I've been wondering for years why print advertisements for movies usually have no content. You get a still image from the movie, the list of the stars, and a few quotes from reviews.

I always discount the quotes from reviews by exactly 100%. The quotes are taken out of context and always positive and thus just noise: "Thrilling!", "An exceptional performance!"

Why not instead use that space (sometimes a whole page of The New York Times) to convey some information about the movie - enough so I can judge if the movie might be interesting?

Give a plot synopsis. Give the first few pages of the press pack that describe the making of the movie.

Even better, include a mobile phone bar code that will take me to a trailer of the movie or the full text of the movie review.

Same thing for books. Take out the blurbs, and put in the text from the jacket cover - or even better, a copy of the first few pages of chapter one.