I agree with all of the above.

But if D&B is a tool in the arsenal, why I have not found a single book about D&Bing a portrait?

As an example, let's say that most of the portrait books agree that a single light on one side of the face gives a certain dramatic effect bla bla bla.

None (that I have found) says that, for example, dodging an "aurea" around a portrait is a powerful technique.