Most use stereo because we have 2 ears... and therefore only 2 channels are necessary for 3D sound. 5.1 is a gimmick. Stereo forever.
That's false. We only have 2 ears, but each of those ears can distinguish sound coming from many different directions because your head and earlobes alter the sound differently depending on where it comes from. You can only try to generate realistic soundfields with 2 channels if you use headphones. You can record sounds with microphones in the ears of a dummy head (binaural recording), or you can try to simulate these effects through headphones. Both of those methods have problems, including the fact that the sound stays the same when you turn your head.
By your reasoning, we should only need 2 pixels on a TV since we only have 2 eyes.
Happiness is twin floppies.