A mono center channel suffices because vision dominates perceived sound location.

Evidence

I get up from my chair from time to time just to satisfy my curiosity because for sounds associated with on-screen action there is the powerful “ventriloquism” effect. We hear the sound coming from where we see the lips move, the gun flash, or the door slam. The hours spent by moviegoers listening to a monophonic center channel as action moves around on the screen suggests that it works very well. Only big budget movies do much panning of sounds across the screen. Why? It costs more to do and complicates the editing process that can sometimes go on up to hours before a film is released. — Toole, Floyd E, Sound reproduction- the acoustics and…, 769

Categorization

• XREF: Connects to the ventriloquism effect in multimodal perception literature and to ‘A Midwife’s Tale’-adjacent studies of sensory dominance — actually connects to classic auditory scene analysis work by Bregman and the McGurk effect.
• SEED: An essay angle: why the ‘sound atmosphere’ of cinema is a cheaply engineered illusion — mono center channel does most of the work via the ventriloquism effect.