Build shared values and beliefs among all levels of people. Better communicate Company intentions to customers and employees. Gaining the Managers' and employees' participation, insights, and commitment to quality and service. If you don't know where you're going, any path will get you there.
Missions are useful things but they are just words.
What is critical is not the word on the page but the process of development which gets the executives at the top into some agreement and alignment and which transfers ownership of the end result to the front-line workers. It will be mostly their own, but influenced by the others. Then they have 5 minutes to run around and ask anyone from another table about their ideas. Questions can be of any subject. It was a fast-paced, highly interactive session where we got 20 sets of 4 to 5 opinions total.