Quite simply the audio mixing for TV and movies is utter shit. You shouldn't need a 7.3 sound system to potentially hear the actors legibly. The stereo speakers built into my TV should be adequately supported, and it is frankly the default set up for most people including myself.

Audio mixing being shit as mentioned by other commenter, but also i don't want ny neighbors to hear everything i'm watching by cranking the volume up just so i dont miss dialogues.