Documentaries are important in many ways. One of the main reasons is that they educate you
A week ago, I watched the documentary "Super Size Me" and I thought that it showed very well how dangerous it is to eat fast-food on regular basis. It affects your body and I don't think many people know that. How could they know it if they aren't going to read studies on how dangerous it is. Not many people have the time, or want to make time, to read a study. It is more fun and effective when you van watch it in a documentary, because an image is worth more than a thousand words. You can also see how it affects Morgan, because if you read about it, you wouldn't be able to see how miserable he was.
Another importance of documentaries is that it can change society. A great documentary that changed the American society is "Race to nowhere". It's about how children try to overachieve at school and they get depressed and some of them even commit suicide. After this documentary was released, it opened many eyes in America. A lot of schools changed their way of teaching, giving the children a "no homework week" once in a while. Without that documentary that would have never happened and many children would still be getting pressure to overachieve.
Documentaries are also important to show the world some urgent troubles in the world, like global warming. I know that every time i see a documentary that shows how global warming is getting worse, I feel guilty and I'm more aware of biking to school instead of going by car. Because even though you know there is a huge problem in the world, like the lack of water in third world countries like Africa, you don't really do anything about until you get confronted with touching stories in documentaries.
So basically, documentaries are very important. They educate, they influence society and they make people undertake action.