Well, consulting is often used because they need an answer to a question. That may be open-ended like:
"What moves should we make to expand our business?"
But other times they just want confirmation:
"Should we merge with Discovery?" (Sure, I guess. Here are some reasons you could. cha-ching)
"Should we split with Discovery?" (Sure, I guess. Here are some reasons you could. cha-ching)
Other times they just need to pay people to give them excuses to lay off people. McKinsey's always available for that.