When you view movie trailers on YouTube or other sites, you often have to sit through advertisements to see the trailer. This means you are watching an ad before you get to the trailer, which is essentially an ad itself. Apple gives you a site where you can watch high-definition trailers without ads. In addition, you can use Siri or Spotlight to go right to a trailer. On iOS, there is even an official Apple Movie Trailers app.
unfortunately iTune Movie Trailers isn't available in Australian Region.