What is the importance of postcards in the story, Unaccustomed Earth?

Postcards are a feature in the short story “Unaccustomed Earth.” Postcards depicting various attractions, cities, and destinations are purchased by Ruma’s father and sent to Ruma and her family as he travels around the world. While visiting Seattle, Ruma’s father purchases a postcard to send to his girlfriend, Mrs. Bagchi, though he misplaces it before he leaves. Akash finds the postcard, which leads Ruma to realize her father does not want to move to Seattle because he is seeing Mrs. Bagchi. Ruma mails the postcard.