Why doesn't my puppy like to go on walks?

He's very young. At his age, he isn't 100% sure he's safe when he leaves home. You may need to carry him to a new place, then sit and stay there for a little while, holding onto his leash. When he's more confident, he'll love going for walks. In the meantime, keep using his leash. Take him a short distance away from his comfort zone at first, then add a few feet at a time. Patience. He's still a baby.