Ever since Daphne Bridgerton became Duchess of Hastings (and actress Phoebe Dynevor exited the show after season 2), fans have been taking every opportunity they can to see her onscreen.
In the books, Daphne’s role becomes smaller after her own story ends, showing her settled life as the Duchess of Hastings. Also, bringing Daphne back without Simon’s character is tricky.