I use obedience for two main reasons. The first is to get a dogs respect and the second is as a calming tool. When we teach a dog to listen to us because we are in charge, not through bribery, we automatically assume the leadership position. This simple change can help so much in our daily lives. Submissive dogs display fewer behavioral issues than dominant dogs and happier lives result. My biggest goal when working with dogs and humans is to teach people that obedience and behavior modification are two completely different things, but can be used together to get phenomenal results. When we teach a dog to sit, down, come, or stay using these techniques they usually learn it very quickly, but what does that really help. The action that we just taught them is now an excitement tool; the dog performs his trick in order to get a reward and ends up more excited than when he started.
Do you want to have to offer him a treat to listen, or do you want him to lie down at any point for any reason with any distraction around?
Think about it, when you tell your dog to down, do you want him wagging his tail and squirming in place barely able to control himself, or laying there contentedly waiting for you to calmly release him?