The short answer to why the title of a book may not be protected by copyright is that the law says it may not
Are you sure about that, Father Steve?
What about a title which consists of, or includes, an original coinage?
No example springs immediately to mind - other than a title, "Exxoneration", which is the only thing memorable about that particular work - but I'm sure others will think of better examples.
Many titles are simply descriptive and, therefore, not distinctive for copyright purposes. Others are drawn from well-known sources (example, a line from Shakespeare) and, therefore, make no pretence to originality.
But, to say an author cannot enjoy copyright in his own original coinage, whether it appears inside a book, or on its cover, is a startling proposition, Father Steve, and it offends my sense of natural justice. [Not to mention my litigious pretensions. I once had a title "Tongue Fu" stolen from me.]
May we have your citation for your legal proposition, Father Steve?
BTW the law allows one to quote from a copyrighted work for cataloguing or review purposes [with restraint and appropriate credit], whether the quote appears inside or on top of a book.
