Step-by-step explanation:
In Chapter 2 of The Great Gatsby, Catherine explains to Nick that Tom and Daisy are not getting a divorce because Daisy is Catholic and doesn't believe in divorce. However, this seems to be an inaccurate explanation since Tom has also been unfaithful to Daisy multiple times and it is hinted that they are staying together due to social and financial reasons rather than religious beliefs.
The real reason behind Tom and Daisy's marriage is not explicitly stated in the book, but it can be inferred that they are staying together for appearances and the preservation of their social status. The rumor about Daisy being Catholic might have been spread by Tom himself as a way to deflect attention from his own infidelity and avoid any potential scandal.