Final answer:
The narrator in 'Araby' does not buy anything for Mangan's sister due to a blend of arriving late at the bazaar, which was almost closed, and becoming disillusioned with the mundane and vulgar reality that contradicted his romantic expectations.
Step-by-step explanation:
The narrator does not buy anything for Mangan's sister in Araby because his dreams and desires are crushed by the bleak reality of the bazaar.
The narrator arrives late when most of the stalls are closed, and he is disillusioned by the conversation of the vulgar saleswoman talking about a dance. This situation, along with his realization of the mundane aspect of the event, contrasts sharply with his romantic and idealistic perception of the East and his quest to get a gift for Mangan's sister.
The epiphany that the narrator has underscores the theme of disillusionment and the contrast between the ideal and the real, being one of the central motifs of James Joyce's coming-of-age story.