There's an old saying that ' a consultant is someone who borrows your watch to tell you the time and then charges you £50 for the privilege' , something that will strike a chord with many business people. Although this is an 'anti-consultant' line it does illustrate what many managers use consultants for.
I've lost count of the number of times I've been told by a manager that 'Everything you're saying I've already told the management - they won't listen to me, but they will listen to you because they're paying for your advice'. The reason this works is that companies tend to assume that their employees have their own agenda when they recommend change - and see external consultants as providing an objective view of the world.
I think this external view is something that we should promote in a psoitive way - after all it's our knowledge of a range of companies and approaches to problems that is our stock in trade.