Over the last century, every single line of a screenplay has become standardized to make reading, analyzing, and comparing scripts as efficient as possible. The formats also differ between sub-industries—Broadway has their own, as does the BBC, as do American sitcoms. Scripts are read by dozens of people as they go through the production process, from casting agents to art directors to studio executives. The standardized formats help everyone estimate how long the finished show will be, tells the basic story as clearly as possible, and has lots of room for people to write their own notes in the margins. 99% of studio executives will instantly trash a spec script that does not follow the correct format. Same for screenwriting competitions. The number one purpose of screenwriting software is to help you use the proper format. They all do this, but Final Draft does it better than anyone else.