You are asking to be what it is not. It is not personal protection training, military training, or what have you. It is a specific sport that most people do for fun. But it is also used as a breed survey. If a dog can succeed at a high level in sch it shows the dog is capable of producing some offspring that will contain the qualities required for PP/K9/Military.
Essentially what your question comes down to is why do any dog sport? What good is dock jumping....oh so my dog can retrieve a ball by jumping off a dock! woohoo! But maybe with some additional training and proper breeding it could be used to develop some great hunting/retrieving dogs.