Gatsby's love for Daisy is ultimately doomed for a number of reasons. Gatsby believes that it is possible to repeat the past, and he unrealistically expects that he and Daisy will simply resume their romantic relationship right where they left off, as if all that happened in the years...
Gatsby's love for Daisy is ultimately doomed for a number of reasons. Gatsby believes that it is possible to repeat the past, and he unrealistically expects that he and Daisy will simply resume their romantic relationship right where they left off, as if all that happened in the years they've been apart—including the war and her marriage to Tom—never happened. Such a thing is simply not possible; by the time Daisy and Gatsby reconnect, too much has changed, and Daisy has moved on with her life. She married Tom, and they even have a child together. Though their life is certainly far from perfect, it is familiar and comfortable to her.
It's also worth noting that despite his apparent desire for her, Gatsby's does not seem to truly understand or empathize with Daisy, and as a result, he is shocked when she refuses to say that she never loved Tom:
"Oh, you want too much!" she cried to Gatsby. "I love you now—isn't that enough? I can't help what's past." She began to sob helplessly.
"I did love him once—but I loved you too."
Gatsby's eyes opened and closed.
"You loved me TOO?" he repeated.
Gatsby appears wholly unconcerned by the gravity of what he is asking Daisy to do, and his lack of regard for the life she has lived since they parted suggests that he is more interested in the fantasy of Daisy that exists in his dreams than he is in the real, flawed person that stands before him. Ostensibly, Gatsby's pursuit of wealth was to secure Daisy's love, but by the time they meet up again, it seems that Gatsby has come to see Daisy herself as a commodity he must possess.
Daisy's feelings for Gatsby also appear to be shallow, which explains why she is unwilling to leave Tom. Daisy is a status-conscious person, and at the end of the day, she and Gatsby do not share a similar social status. Despite his wealth, Gatsby is essentially a criminal. He has made his fortune illegally by manufacturing, distributing, and selling alcohol during the Prohibition Era, and Tom also suggests that Gatsby may be involved in some other illegal, and less easily excused, activities—a revelation that seems to frighten Daisy away during their big confrontation in the city. Daisy is used to a very particular and not easily attainable lifestyle, and she absolutely cannot continue that lifestyle with Gatsby. Tom and Daisy are both from old money, meaning that they enjoy a level of privilege, power, and status that Gatsby, with his new money and humble past, does not. Gatsby may be rich, but in choosing him over Tom, Daisy knows she would lose her lofty social position, and ultimately, she is not willing to risk it.