Actually, there's a very simple reason: almost all contest winners & finalists aren't quite good enough yet. That doesn't mean that they won't ever be good enough, but in most cases they lack the experience and seasoning needed at the pro level. Think of writers as baseball players: it's almost unheard of for someone to go from high school onto the roster of a pro level team. Baseball players work their way up through the minors (screenwriting contests) until they get called up (find representation). Then they sit on the bench, go through training camp until the coach (production executive) thinks they're ready and an opportunity to perform emerges.

In a perfect world, great scripts would rise to the top. May I suggest Hollywood is not that perfect. Why haven't contests uncovered truly great scripts? And why do we often scratch our heads at the ones that win? Everyone wants to believe that contests pick the best scripts. But strange things happen. Scripts place well in one contest, but not at all in another. And you will hear stories of an old script that wins whereas a newer, better script doesn't even place. Why??? Let's say you have a really great script. You really don't want to trust it to a contest -- because look what usually wins. But let's say you do send it in and the reader loves it. Wow. Great concept. Great ideas. He's got a million dollar script in his hands. From a nobody... Like finding a million dollars lying on the sidewalk...

Are you saying a reader may love your script and steal it? Isn't that what copyrighting is for? Or maybe you've lost me.

I don't think it's a matter of picking the best scripts. I believe that contests and producers are looking for different things.

imho, screenwriting contests are basically auditions for writers.

All the contest claim they're looking for the best scripts. That's the lure they use. Instead, they seem to choose writing samples.

(There are exceptions. This year, two Nicholl finalists had to drop out because they sold their screenplays.)

A lot of the scripts that win are not necessarily commercial. Hollywood likes to make high concept flicks with a lot of whiz bang flash -- and that's not always the best vehicle for showcasing a writer's talent. Smaller, quirkier, more character and dialogue driven... those kinds of things can work in a contest. That's why certain contests are starting to differentiate themselves as to what they're looking for, including some that now focus on high concept scripts.

Screenplays are blueprints for movies. What's the point of showcasing you talent for screenplays that will never get made. Write a novel.