One reason I can see not repeating title or sub title words in the keywords field is that you get only so many high - value opportunities. (authorimprints.com)
In 1990, I handled the production (i.e., I worked with the author, copy editor, and indexer; I did the design and typesetting) on a book for John Wiley titled WORD OF MOUTH MARKETING by Jerry Wilson. (writerunboxed.com)