The party given by Gatsby in Chapter 6 seems different to Nick. Why is that?

The painfully awkward luncheon party at Gatsby's mansion underlines the hostility of the American 1920s toward the figure of the self-made man. Both the Sloanes and Tom Buchanan treat Gatsby with contempt and condescension, because he is not of the long-standing American upper class. Though Gatsby is fabulously wealthy, perhaps wealthier than Tom himself, he is still regarded as socially inferior. For Fitzgerald, nothing could be more inimical to the original ideals of America. The first Americans fought to escape the tyrannies of the European nobility; Tom Buchanan longs to reproduce them.