This was a very interesting question. In fact, not all fairy tales and novels ended with a prince and a princess together, but it was one of the most common endings. This was because in fairy tales and novels, princes and princesses were usually the main characters and the focus of the story. Therefore, when they were together, the story would become more vivid and attractive. Of course, other than the prince and princess, knights were also important characters in the story. In many cases, knights were used to represent justice and courage. They were usually the ones who protected princesses or princes. Therefore, the outcome of knights was often similar to that of princes and princesses. Knights were usually heroic characters in fairy tales and novels. They usually had excellent martial arts and generous qualities, so in some cases, their ending might be similar to that of princes and princesses.