We believe, for example, that polls have consistently shown that the majority of Americans do not believe that the Warren Report really brought out the truth, whatever it may be. The same can be said about many other such commissions and inquiries.
We seem to have accepted, until the recent development of the Internet, that government "inquiries" are entitled to obscure as much as they reveal.
Sometimes these things are more of a culture of resistance to truth when it is inconvenient rather than an active conspiracy to cover up.