I will not post my exact response for this question, but be ready to answer it for any consulting firm. Consulting is a much different business than others simply because you will be involved in so many industries. Thus, it is necessary to describe reasons that are relevant to the consulting industry (i.e. data mining, dissecting business parts, etc). Further, why do YOU want to do this type of work? Firms need to know that they'll be sending someone on the road that is going to let their enthusiasm for solving complex business problems show to the client.