Why did Angus tuck say they were like rock beside the road?

In "Tuck Everlasting," Angus Tuck uses the metaphor of being "like a rock beside the road" to express the idea of being unchanging and enduring. Just as a rock remains stationary and unaffected by the passage of time or external circumstances, the Tuck family experiences a perpetual existence due to their immortality. This comparison highlights their isolation from the natural flow of life and death, illustrating the consequences of their eternal condition.