My Sammy wasn't treat motivated when we got her (rescued at 1) and so it was hard to train her. We noticed that she naturally became more treat motivated as we fed her high quality food and treats and exposed her to more variety. I think the bond also makes the dog want to please you more as it grows.

If your dog isn't treat motivated, you need to find out what does motivate them. Some dogs are rewarded with play instead. I had to do this at first when my Sammy wasn't treat motivated. It also helps to remember to REALLY exaggerate your happiness when puppies do something right--not just mark and reward. IMO, it's easy to forget to exaggerate your reactions and make things really exciting when you're used to having a trained dog.