There's actually a very prosaic answer to this question. When we listen closely we tend to look in that direction. Ears on each side of the head, duh. When we record we do the same. Maybe there are groups the performers occupy different locations around the room at random. Not many, is my guess. From intimate solo singer to full orchestra to U2 extravaganza the performance always occupies a relatively small area in front of us.
Anything way off to the sides is therefore much more a gimmick or effect than music.
There. Done. And on to the next question. ....
Once again, the mic techniques used for classical recordings are specifically designed to capture information from well beyond a 'relatively small area'. Not just side to side, but deep too.
Google something like the following "Decca tree recoding an orchestra" or "how to set up mics for recording an orchestra", or similar verbiage.
Take a look at this diagram below and let me know why this mic placement for the San Francisco Orchestra, will only produce a soundstage that 'occupies a relatively small area'.
http://www.linkwitzlab.com/Audio_production/sf_symphony.htm
Why am I getting the idea that many people here, have not spent a lot of time listening to classical recordings on a good system?
My system, in my relatively small room, consistently produces a soundstage of an orchestra, that sounds about at the same scale as if I was about 20 rows back at Disney Hall. Not trickery, no gimmicks, no false large soundstage created by early reflections, etc. Simply the soundstage captured on the recording by tried and true recording methods.