Here's why the author chose to portray them this way:
* To emphasize their timelessness: The Tucks have been living for over a century and have remained unchanged. Their speech reflects their connection to a bygone era and highlights their "unstuck" nature in the modern world. Their dialect is like a window to a past time, a reminder that they haven't moved forward with the times.
* To create a sense of mystery: The unusual way they speak adds to the air of secrecy and wonder surrounding the Tuck family and their secret of immortality. Their language feels both familiar and strangely foreign, making them seem like outsiders, further adding to the intrigue.
* To highlight their isolation: The Tucks are a family who has chosen a life apart from the world due to their immortality. Their speech reflects their deliberate separation from the mainstream, setting them apart from the other characters in the novel.
* To add a touch of whimsy: The Tuck family is often characterized as being playful and lighthearted, even in the face of their unusual circumstances. Their speech reflects this, with a slightly playful tone and some quirky word choices.
Overall, the Tucks' unique dialect is a powerful tool that Babbitt uses to build the story's atmosphere, to create a sense of mystery, to emphasize their timeless nature, and to reveal their isolation. It makes the story feel like a fairy tale, a fantastical journey that is both captivating and intriguing.