This, and the tendency for company leadership to feel outsourcing means they can offload all responsibility for project success.
Something I've seen firsthand is companies that are pathologically incapable of making important decisions internally, and that is why they bring in a consultancy. Consultants go around to the various stakeholders (who can't agree on anything), gather requirements from each, then make recommendations. Despite the fact that the recommendations are basically a micro-model of the stakeholders' existing points of view and the result is the same no-win scenario the company was facing to begin with, the recommendations are acted upon, either in whole or in part. When the result is the same mess that would have inevitably happened even before the consultancy was brought in, at least now it's the consultants' fault that their recommendations didn't work out. Managers can then stir up a big stink when it's time to renegotiate the contract, they win some petty, unimportant concessions from the consultancy, and it's time to rinse and repeat.