It's safe to say 100% of the audience members know the name of the movie they're attending and don't need to be reminded in big letters on the screen.
The movie is also presented in Television and most of the times people don't have access to the movie name they are about to watch. So they see the name in the openning credits/title.
Also according to Wikipedia
In a motion picture, television program or video game, the opening credits or opening titles are shown at the very beginning and list the most important members of the production. They are now usually shown as text superimposed on a blank screen or static pictures, or sometimes on top of action in the show. There may or may not be accompanying music. When opening credits are built into a separate sequence of their own, the correct term is title sequence (such as the familiar James Bond and Pink Panther title sequences).
So just to finish the presentation with the names of the members of the production in style, they finish with the movie title.
Movie Sequels or Prequels are also better identified by the title in the beginnining.
Also you can tell a lot how a movie is gonna be by the style and art of the openning title. Take for example Oblivion:
You know it's gonna be a futuristic action type movie just by the title.
BTW The openning movie titles always gives me the chills.