I loved this story mainly because it looks at a common phenomenon — separation — from a new and less common angle: it focuses on the process of telling others (especially the children) rather than on the reasons behind the separation itself.
We see that although the idea of separation is Richard’s, it is Joan who plays the reasonable, composed role in the process. She handles it very well, while Richard — along with the two sons — seems more emotional in dealing with the situation compared to the women.
Throughout the story, there are hints that Richard has another woman in mind, and that this relationship probably played a part in his decision to leave Joan. However, Updike deliberately focuses less on scandal and more on the emotional confusion, guilt, and emptiness of the decision. In fact, he very artistically shows that in most real separations, there is never just one reason.
That is why, when Richard’s son asks “Why?”, it is not an easy question to answer: in real life, “why” is messy, not dramatic.
This quiet, painful complexity is what makes the story feel so real and heartbreaking — rather than like a soap opera.