This is a question I get asked a lot. Here’s my elevator pitch reply (can you improve on it?):
Maps improve Situational Awareness by revealing where you are now and where things are heading. They provide:
1/ alignment around a common goal (customer needs)
2/ a visual aid for communicating with (sometimes conflicting) stakeholders
3/ a diagnostic for reducing costs associated with duplication
4/ a platform for strategic thinking and
5/ a guide for organisations to adapt to and exploit changes in the environment.