How does the poet make "Because I could not stop for Death" a disturbing poem?

If "Because I Could Not Stop For Death" is a disturbing poem, perhaps it is due to the portrayal of death as a sort of implacable gentleman who silently insists on the company of the poem's speaker. He does not exert any force or cause pain, and he is patient, taking his time to guide the speaker "toward eternity." The journey to death is described as a carriage ride past familiar, comforting sights like the schoolyard and fields of grain. When the destination of her body is reached, the "house" he delivers her to is her grave. She remarks that this all happened centuries ago, but the passage of time in eternity is apparently so swift that it seems as short as the day she figured out that her time to die had come.