Consider that if they study the problem they may discover the problem is severe and they can't fix it. Now they have an even more serious problem: If they lie about the existence of the report, they're defrauding advertisers. If they admit the contents of the report, advertisers and users will flee.

So it's rational for them to not look in the first place. If they don't know, then they're not technically lying. This is good for them, but nobody else.