It invites justification. The question 'why' directs the listener's attention backwards in time, to what has already taken place. In the context of a desired result in the future, backward directed attention has limited use. To find the intended purpose of a course of action, one needs to ask what the action is for. They contain an element of action, of purpose, of forward momentum and direction.
Intent is presupposed, and information is brought into the system to facilitate action.
The answers to these questions are largely a matter of personal choice. With the 'avoid at all costs' class, the first thing to ask is what we would rather have in place of the disaster, and then go on to refine it into something highly desirable. When defining evidence of the desired outcome, it needs to be something that another person could see, hear or feel if it were pointed out to them. That is the meaning of sensory based evidence. Abstract concepts can be described in sensory based terms.