@bruce19 Your example of recording a solo guitar and singer illustrates my point perfectly but not in the way you may have thought. I've recorded hundreds of tracks of singer/guitar and I've tried a range of microphone setups and locations. If you want to attempt to recreate what you would hear if you sat 10' away from someone singing and playing the guitar you might think that one or two microphones placed at your listening position would do the trick. What you will find is that this setup sounds flat and lifeless. Your interpretation would be that this is a crappy recording even though, theoretically, it should most closely match what you heard.
In order to achieve the sound one might expect to hear when you get a professionally produced and recorded album I would use two different mics for the guitar - one condenser mic about 6" from the sound hole, and a second mic about 4" from the fretboard. I would use a third large diaphram condenser mic for the vocals but I would nearly always record the vocals separately from the guitar tracks so the vocals and guitar don't bleed into the other tracks.
Once the tracks are recorded I would do the mix. Mixing would include EQ'ing each track, adding delay and reverb custom for each track for a pleasant "room acoustic", and then adding any other effects on the whole mix.
The result of this process is to create the illusion that you are sitting 10' away from a human playing an acoustic guitar and singing. It is an artificial facsimile of what you think you heard in the real world.
To be fair, there have been thousands of great recordings using a minimal number of microphones in a carefully controlled acoustic space. This is really hard to do and impossible even in most recording studios. On the other hand we can hear what this technique sounds like for singer/guitar on old blues recordings. These used a single mic with no EQ or processing. By today's standards they don't sound very good.
My point still stands that the vast majority of recordings do not attempt to recreate live sound from a single listening point. People simply wouldn't buy them because they don't resemble what we now think of as "high fidelity."

