Text Mining - Document Metadata included in processing

I am teaching a module on text mining next week, so I am finally diving into workflows to help teach the fundamental concept.s

The concept of documents having metadata like author, date, title, etc., is fantastic. However, I have to admit that I do not understand the intuition behind the decision to include these elements in downstream preprocessing steps like Bag of Words, Term Frequency, etc.

Am I missing a setting (or overall pattern) so that the column we identify as the document is the only thing included in the text cleaning steps?