Movie Previews

What the heck is wrong with movie previews these days. They slowly show more and more of the movie before we even get to see it. Sometimes I see the preview and go "well that was a nice movie!" Alfred Hitchcock was famous for having previews for his movie where he just appeared before the screen and tell the gist of the upcoming movie. He would even tell everyone not to talk about certain movies so not to spoil it for others. Now we have specials on TV where they show enough clips of the movie to cover half of it. I understand the need to promote the movie but what really are we paying the 7 dollars for? It seems like more and more these days we are paying for these previews before the movie we have already seen.