It could be a very unique and metaphorical expression in the novel. Maybe the 'good soup' represents something stable or homey, and 'not picking up the phone' implies a detachment from the outside world or modern distractions. It might be used to set a certain mood or character trait within the story.
The 'good soup never picks up the phone' might be a creative way for the author to introduce an element of mystery or quirkiness in the novel. It could be that the soup is personified in a way, and not picking up the phone is a characteristic that differentiates it from the more 'active' or 'connected' elements in the story. This statement may also be used to foreshadow certain events or character developments, like perhaps a character who is more like the 'good soup' will choose a path that is less influenced by modern technology and more focused on inner peace and traditional values.
In the context of the Korean novel, this statement might be a cultural or idiomatic expression specific to the story's setting. It could be that the soup is a symbol of comfort and tradition, and the act of not picking up the phone is a way of showing that the character is more in tune with the simple, traditional things rather than the hustle and bustle associated with modern communication devices.