Innovation is a Post-Problem
Problems are solutions waiting to happen, solutions the other guys haven't quite noticed yet. Some of the most brilliant designs in history were simply the way around an existing problem, elevating our lives and our cultures.
Mind-mapping allows us to kick out as many ideas as possible in a very short time period, with a tremendous variety of results. We then refine these into fewer and better ideas before even starting to sketch. This isn't pointless design. We ask why, and we use reason. We like things that make sense.