Why did Daisy stay with Tom?

****SPOILERS**** For anyone who has only seen this film version and is not familiar with the novel, there is as another poster suggested, a strong possibility that Tom is physically abusive to Daisy and would not be willing to let her go. Also, Daisy was expected to marry old money and even with Gatsby's new found wealth and status, he would still be declared unsuitable by high society due to the way he acquired his wealth and his shady business dealings.

In the book, as well as this film version and the 2000 A&E TV movie adaptation, we as readers and viewers are left wondering just exactly what was in Daisy's heart and mind. Yes, choosing to go back to Tom reflected the influence that his power and old money had over her choices and ultimately, she couldn't forsake that for Gatsby's questionable background and business. She also had a child to think about, and no doubt Tom would have done everything in his power to keep Daisy his wife and possibly would have used their daughter as a way to keep Daisy with him, and I doubt he would let her have custody of Pammy if the did actually divorce. And yes, money was important to Daisy, no question. But she never really pretended to be anything she was not; Gatsby idealized her, put her on a pedestal, and as Nick said, he was living in the past. Daisy was married with a child, a fact that Gatsby in the novel did his best not to acknowledge, even though the latter fact (the child) he saw with his own eyes. He had this fantasy that he worked so hard to try to make it come true, but the reality didn't live up to it. It rarely does.

Back to the novel, it is implied that Nick never sees or speaks to Daisy again after he peers in the window of the house to see her comforted by Tom after Myrtle's death, but he does see Tom again after Gatsby's death. Nick doesn't hide his disappointment and disgust but Tom obviously feels justified and while Nick shakes his hand, you know whatever friendship they may have had is gone. The 1974 film version Daisy appears during this exchange, (which never happened in the book) and she chats up Nick as if nothing happened. Maybe she was putting up a front, but it made her seem vapid and heartless, which maybe is what the filmmakers were going for. I think the scene was unnecessary and I feel it is better to let viewers make up their own mind.

I think Daisy loved Gatsby as far as she was capable, but ultimately, social position and the security of Tom's wealth was more important. I think she loved Tom as well, but of course, his money was the real icing on the cake, so to speak.