We encounter this in literary study of The Canterbury Tales and it is important to recall that the frame narrative (the pilgrimage) implies that the stories are heard by listeners. Also the Tales would be taken in by ear if someone read aloud to an audience from one of the expensive texts available. This affects the composition as more blatant effects are needed, such as the narrator stating clearly when he or she is about to change the topic.
For detailed analysis of many of the Tales, visit my website Classics of English Literature also hyperlinked from this page.