If you fail to plan, you plan to fail. 

In order to attrack financers, you have to have a business plan.  In order to convince vendors to give you credit, you have to convince them you have a plan to pay them back.  If you plan to take your family on a trip, you have to plan the stops, where to eat, and where to stay or your vacation to DisneyLand may result in a trip to Bugtussle.

It's not different in disaster planning.  You need to know where you are and where you are going or you may end up in a disaster with no plan and no business.

As a famous Roman once said, "When danger comes, it's too late to plan".