Mirrors in Therapy?

I read this fascinating article on mood altering ability of mirrors. It says "Subjects tested in a room with a mirror have been found to work harder, to be more helpful and to be less inclined to cheat, and less likely to judge others based on social stereotypes about, for example, sex, race or religion." Basically, they make people more self aware, and not just at a surface level. Physical self reflection encourages philosophical self reflection. People reflect more, are more aware of their effect on other people, and are more aware of other people's opinions when a mirror is in the room. What strikes me is these are all things that therapy encourages, yet I have never heard anything about mirrors in therapy, and I have never been in a therapy room with a mirror. I would imagine a mirror that the client is staring at while they are sitting could be very distracting, but an indirect mirror could subtly enhance what is already happening in the room.