Sometimes you need to discuss your idea with others though to see whether they think positively about it. Otherwise you start blindly and don't know whether there is any audience for your idea.
White papers are a first starting point, but nothing more. Sometimes it is even only a starting point for the actual team which then, after finding weaknesses in the initial design, deviate from the original and build an even better protocol.
Yeah, not all investors are focusing with the creation and contents of its whitepaper, more people are focusing with the whole package of a project and how they will implement all their features and plans.