You definitely touched on the key aspect of these types of exercise and evaluation: motivating participants after the fact to improve. In my experience large scale exercises are key to show deficiencies, and often times respective section heads are motivated after an exercise to seek out grant funds for trainings and equipment once they realize they are lacking it. Sometimes disaster training is something that is neglected due to budgetary constraints, and excersizes like this also help justify costs to decision makers such as county commissioners, city officials, etc. So, excercises serve manifold purpose, develop skills, highlight shortfalls, motivate improvement, and enlighten those that control funding