Well three words: They don't work. Not for regular people. Yes, I can hear it now, you must use it correctly. Frankly, the only people I have seen do that are trainers, and in every case the dog yelped in pain. So if you are ready to apprentice for 10 years AND cause your dog pain go for it.
Beyond that I do have another reason, my approach is based on building a relationship with your dog so your dog enjoys working for you and actually wants to be with you. This is not for everyone, there are those who want the dog to be an automaton. If you are one of them, there are plenty of trainers out there who will help you use pain and force to create that kind of dog. That is not what I do.
