Why do all of our family dog classes advance to working at parks, restaurants, shopping centers? We teach you how to help your dog generalize their training in many different areas working up to higher distraction areas. Along with that, teaching all the different kinds of reinforcement you can use besides treats to help your dog realize how valuable you are to him, causing him to want to work for you! If you don't generalize, your dog may not be properly trained!
http://3lostdogs.com/why-you-cant-get-your-dog-to-listen-to-you/