Neither parent however recognizes that Fern may be telling the truth, until Charlotte begins spinning words on her web. While Fern's uncle and aunt provide her with the opportunity to form friendships with the animals in their barn, they nevertheless also adhere to the utilitarian view of farm living. Farm animals are born and raised to serve human life, and not to provide friendship. Hence, Wilbur is fattened to become the Christmas feast. Fern is deeply involved in this life and death struggle, while the adults have no inkling of what is happening.

When Charlotte spins words in her web, Wilbur is on his way to salvation. Still, the uncle and aunt, as well as the other adults, regard this as a miracle rather than an indication of actual intelligence in the animals. Wilbur is once again used for human gain when he is taken to the fair. Here the roles are reversed, and Charlotte dies, with the difference that Wilbur can do nothing to save her. Her children survive however...

Charlotte is with Wilbur at all times, while Fern is of necessity bound by the schedule of her human life. At the end, the author indicates that Fern's visits have dwindled to a stop as she grew up.
In this way, both Wilbur's friendships to Charlotte and Fern indicate that the cycle of life and the cycle of friendship are temporary phenomena. Fern grows up to join the world of the adults around her. This separates her from the fantasy world of the animals. Charlotte in turn had a limited life expectancy, and succumbed to death, which also separated her from her friendship with Wilbur. In the end however, it appears that the author establishes this as the natural state of affairs: children grow up and friendships end, but memories last for a lifetime.