Lightroom, Photoshop and ... Bridge?

I have just had a good look over Stephen Laskervitch's book Photoshop CS6 and Lightroom 4. It seems very good. My main question stems from his dedicating many pages to Bridge without, it seems to me, stating any reason for using it if one already uses Lightroom. I'm sure there is a reason, but I'm a little slow about these things. Any words of wisdom?