An area feels bigger if there's nothing to stop the eye. In this example a pair of daybeds is used instead of sofas. Because the daybeds have no backs, the eye can see past them into adjoining spaces, making the room appear larger.
The same theory applies to coffee tables. Because the coffee table in this room is transparent, it takes up less visual space. And to make the room appear taller, curtains were mounted near the ceiling, drawing the eyes upward.