Here's why:
* The raven's constant refrain: The raven's repeated utterance "Nevermore" serves as a relentless reminder of the narrator's loss and the impossibility of bringing his beloved Lenore back. This keeps his sorrow fresh and prevents any possibility of healing.
* The narrator's internal dialogue: The narrator's desperate questioning of the raven shows his increasing desperation and inability to accept the finality of Lenore's death. He grapples with the pain of loss and the impossibility of escape.
* The poem's ending: The final lines of the poem reveal the narrator's surrender to despair, trapped in his grief with the raven's haunting presence.
While the narrator might initially hope the raven will offer him solace or answers, the bird's constant repetition of "Nevermore" ultimately fuels his despair, leaving him with no escape from his sorrow.