In the beginning, I will believe that if you are deceived then you will not believe or say that you will be more cautious. White papers can also be imitated. All things can be spent to make you believe that it is true. All can't just look at the white paper.
Just like other people said, they consider the white paper as one of the best requirement by seeing the legitimacy of a project. However, sometimes those things that they write in whitepaper are not true. Whitepaper might become obsolete and the objective can change as the time passing by.