Here's why:
* The poem is a fragmented dream vision: The speaker is not a specific, identifiable character. He exists within the dream-like world of the poem, where the boundaries of reality are blurred.
* The speaker's identity is not crucial to the poem's meaning: The poem's focus is on the fantastical world created by Kubla Khan and the powerful images and emotions evoked by that world.
* The speaker could be seen as a representation of the poet himself: Coleridge's own creative process and the influence of opium are heavily implied in the poem, suggesting a connection between the speaker and the poet's subconscious.
Therefore, while the speaker remains unnamed and somewhat undefined, he serves as a conduit for the poem's vivid imagery and the exploration of themes like creativity, inspiration, and the power of the imagination.