Here's why:
* Rachel's primary love interest is Shinichi Kudo: Throughout the series, Rachel is shown to have strong feelings for Shinichi (who is trapped in the body of Conan Edogawa).
* Jimmy Kudo's focus is on solving cases: Jimmy, as the protagonist, is mainly focused on solving crimes and helping others. While he cares deeply about Rachel and sees her as a good friend, a romantic relationship isn't a major part of his character arc.
* The story focuses on the mystery: The series revolves around the mystery surrounding Shinichi's disappearance and the ongoing battle against the Black Organization. Romantic subplots are generally secondary to the main plotline.
While a romantic relationship between Rachel and Jimmy is not a key aspect of the story, they have a strong and supportive friendship. It's possible their dynamic might evolve in the future, but for now, the series' focus remains on solving mysteries and unraveling the truth about Shinichi's case.