Many organizations, especially large ones, are very slow at making decisions, even if they ultimately make the right ones. Bringing in people outside the hierarchy to synthesize a great deal of info from across the org, and give upper management the insight to make a decision quickly (and, depending on the engagement and the firm, also implement it) is very often worth the bill at the end.
I will not pretend all of the work we do is 100% the most urgent work all of the time, but I have helped make the sausage for a number of years now, and despite the usual disparaging comments in this thread, it really is often an intellectually rewarding environment where you work with smart colleagues and help people solve real problems.