I have heard tales of the dog that does not like treats. I have yet to meet this dog and in my time as a pet sitter/dog walker I have met hundreds of dogs. All of them have liked treats. They may not have liked a certain type or a certain flavor of treats, but they all liked treats. Even the dogs that were the pickiest of picky eaters would take treats.
The people that tell me that dogs don't like treats are normally those pushing a punishment based form of training. And here is why I say they've learned a skill and know very little about dogs themselves. Dogs are not difficult creatures to understand partly because they are so much like us. Think of treats for dogs as you would money for humans. If I were to offer you a nickle to wash my car you'd likely tell me where to go and what to do when I got there, but if I were to offer you $50 I'd have a much better shot at getting my car washed. Dogs are much the same. Some dogs might not like dried up wheat based garbage treats but offer a dog a liver treat and you're likely to get a reaction.
It is also important to understand that treats won't work in all situations and that is because of other motivating factors. Let's say you're on a date with a person you are very attracted or attached to and I make the offer of $50 to wash my car. Now the response is going to be much the same as if I offered a nickle, because I am now competing against another, more powerful, motivating factor. Your dog is much the same way. They will likely ignore the treat you are offering to chase a squirrel or go play with another dog because those activities offer a much better reinforcer than the treat that is being offered.
There are other situations in which treats won't work. Mainly situations that cause stress or fear in a dog. That is why it is important when training a dog to do so in a calm, relaxed environment. Imagine I make the same offer of $50 for you to wash my car but this time I do so with an AR-15 aimed at your head. You are most likely going to run away or cower before I even get close enough to make the offer. If a dog is fearful it is best to start with classical conditioning and use treats to have them associate your presence with something positive by tossing them treats and leaving then removing yourself. Always let a fearful dog make the choice of when to come up to you.
When a dog doesn't like treats there are very often other factors at play, and understanding dog behavior is important in understanding dog motivation. Every living organism on the planet is motivated by food. Otherwise they'd be dead. There are other things that will motivate a dog and in some dogs those motivating factors could be stronger than treats. If you have a high prey drive bread then perhaps toys that squeak like a freshly captured critter will motivate them more than treats. I've taught dogs to not jump up on my and sit with nothing but attention and pets. The true goal of training a dog with positive reinforcement is to make the successful completion of an activity motivation in its own right. All dogs are unique with different personalities but the underlining biological truths can only move along a spectrum and not disappear entirely. For that reason it might appear a dog isn't motivated by treats when in reality the right treat simply hasn't been found yet, and some dogs might be more motivated by play or attention. Just like some people aren't motivated by money but would rather have happiness or love. Dogs in many ways are just smaller furrier versions of us.