Why do you think the narrator conceals the real cause of Loulou's death?

It is strange that the narrator doesn't tell us the real cause of Loulou's death, but only tells us the various speculations that the characters have of the death. Since Flaubert is writing the story, he can certainly write the cause of the bird's death if he chooses. However, in real life, without a modern autopsy, people can never really be certain about what causes death. In this way, the description of Loulou's death is extremely realistic.