Perhaps it's just me, but are we really thinking about what some of us are saying, here? When was the last time anyone heard a stereo recording where sounds emanated from EITHER the left or right speakers..? Perhaps in stereo's earliest days, when complete separation (or as close to complete as LP's could achieve) was exploited as a gimmick, but it soon disappeared, and stereo got down to the task of recreating the WHOLE soundfield, not just the edges.

So the task of each speaker is not to just play what few sounds might get panned hard out, but primarily those within the soundfield. Plus, it's not JUST intended to give a detailed accurate sound 'picture' when one sits optimally in the 'sweet spot' (basically, an equilateral triangle with the speakers, which BTW indicates that the wider the speakers are placed, the bigger the 'sweet spot'), but anyone almost anywhere in the room other than right next to one speaker or another will get an enhanced feeling of spaciousness, as left and right speaker waves arrive at the ear at different times (not to mention bouncing off room surfaces at different times).

Stereo is FAR more complex than 'left out of the left speaker, right out of the right', and I suggest that, if any of this interests you, you do a FAR more detailed study of the technique before grand theories are put forward with little more than advertising hype and conjecture as basis... Maybe start with Wikipedia and move on from there. I'm pretty positive few if any here are capable of giving a knowledgeable discourse on the difference for stereo perception between a spherical and a planar wave