One of the main reasons why an author would use an excerpt from a text is:
This refers to the use of segments from a text to give additional information or to show some important information from the text. This is in effect a quoted portion from a text.
Please note that your question is incomplete so I gave you a general overview to help you get a better understanding of the concept.
Read more about Romeo and Juliet here:
https://brainly.com/question/1556509