Taking pictures of faces is usually disappointing because the second stage regulator not only hides a big part of the face but it distorts the shape of the mouth and lips into a very uncomplimentary configuration.
Below you see the obvious reason. On the left is a typical regulator with an average 2nd stage and an Air Buddy shown for a size comparison. The center picture shows a woman diver with a second stage in her mouth. On the right is a woman with an Air Buddy in her mouth. If the diver has an Air Buddy on their regulator instead of an extra 2nd stage as is to common now, they only need to switch breathing to the Air Buddy while they are taking pictures.
A second stage regulator does not lend itself to taking picture of SCUBA divers.
The Air Buddy allows your model to breathe while you take pictures.