Most of the people in my opinion start from the fact that even if they get a new original idea, there is someone else in the world that already thought of that. And this is somehow discouraging in going down this road. Also there is the fact that most of the genial ideas mostly are done by people that don't know the specific of that industry as most specialists tend to go over and over on the same path.
Of course, there are many examples that new ideas brighten the world each day, but who defines what is NEW or more exactly might have already been there and only that comes someone with enough resources to see it through...