Instruction Manual
Every movie needs a script. A script is the instruction manual for any movie, as it details every visual and aural aspect of a story. Because so many people are involved in the production of a movie, a script must be presented in a certain format so that everyone will understand it. A correctly formatted script allows the director, cast and crew to all be on the same page when they interpret (and later re-interpret) the initial premise of a story.
Looking Professional
It is quite possible for any aspiring writer with a half decent story to learn how to write a script. Commercial screenwriting software makes it possible for a screenplay to be converted into the all-important format which the studios demand. This is of particular benefit to up and coming screenwriters as any screenplay they submit will immediately look professional. Also, the time saved can be put to good use by learning more about the craft of screenwriting.
Learning the Craft
Successful screenwriters do not tell the audience a story; they show them. What is written is not what the audience will read, but what they will see and hear. A writer may know exactly what their characters are thinking and feeling, but the essence of good screenwriting is in having the ability to convey it on the big screen. As long as a script includes all the pictures, sounds, and dialogue needed to show a story, then it will be on the right road.