Why can't my dogs recognize themselves in a mirror?

Or can they? I’ve just always heard that they do not grasp that it is their reflection or recognize the image as a dog. I have 2 bullmastiffs and even when they are both standing in front of our large mirror seeing each other- a dog they recognize b/c they see them everyday- they are completely uninterested and never focus their eyes on the images in the mirror… just on me pointing at the mirror and they look at me like they are confused! Please explain why dogs cannot see themselves in the mirror, or if my dogs are just a little confused ;)