Writing a screenplay takes a lot of time, energy, caffeine and self-flagellation. Before you start writing, you need to know if your story idea is going to work with an audience.
That means you need to pitch it and get feedback. While someday we hope to have a producer’s undivided attention hanging on every word we say, we need to find an audience for our pitches now before we waste a lot of self-flagellation on a script that nobody wants to read. Friends are good for listening to pitches (they watch movies, right?), but fellow writers are even better if you can find them.