* To highlight the emptiness and superficiality of the Roaring Twenties: The sheer number of attendees and their lack of individuality demonstrate the vapid nature of the parties. They are filled with people who are there for the free food, drinks, and entertainment, but have no real connection to Gatsby or each other.
* To create a sense of anonymity and detachment: The long list makes the attendees seem interchangeable, emphasizing the superficiality of their relationships. It also emphasizes Gatsby's loneliness, as he stands alone in the midst of all this revelry.
* To foreshadow Gatsby's isolation: The list emphasizes that Gatsby throws these lavish parties hoping to attract Daisy, but the guests are never truly invited, and Gatsby remains detached and alone.
* To create a sense of spectacle and extravagance: The sheer volume of the list itself contributes to the overall feeling of extravagance and over-the-top indulgence that permeates the parties.
* To show the contrast between Gatsby's dream and reality: Gatsby desires connection and love, but the vast and impersonal nature of his parties underscores the impossibility of finding it amidst such artificiality.
In essence, the long guest list is a powerful literary device that serves to expose the shallowness and hollowness of the Roaring Twenties, highlight Gatsby's loneliness and the ultimate futility of his dream, and create a sense of overwhelming spectacle and artificiality.