Pictures tell stories. As a story has context, a photograph has more than one focal point.
To me, black and white photography frees the artist from a cage of color in order to tell more complete story. A picture of a sunset is no longer just a pretty picture when the focus is removed from the colors and on to the context found within the background and other content.
When I capture black and white photography, be it a portrait or otherwise, my focus is not on the face, but on the contextual. I want the clothing and the setting to tell the subject's story. I want viewers to get visceral feeling from the textures captured.
For me, a photo is often not really about the subject or about the subject's actions, but more about being a part of the world the photo is of.