Why is Stana Katic leaving Castle?

Stana Katic's departure from "Castle" was primarily due to contract negotiations that did not come to fruition. The show's producers decided to move forward without her character, Kate Beckett, as part of a creative decision for the series' eighth season. Katic expressed gratitude for her time on the show and the opportunity to portray Beckett, while fans were left surprised by the news.