Speakers "Disappearing"

If a given recording is panned fairly hard left and right, then most of the instruments will appear to be coming from the general location in which the left and right speakers are situated.  But this is really coincidental.

Disappearing essentially means non-localizable.  With a full classical orchestra, the first violins should (normally) equally occupy a swathe of the half-circle in front of you that starts outside the left speaker and continues, with equal volume/intensity, to somewhere inside the left speaker.

Pulling speakers further out into the room is the single best improvement in placement one can make.  Bass reinforcement be damned!

Showrooms are particularly bad in this regard.  Almost always they have the boxes jammed back, partly to avoid punters tripping over them, and partly, I suspect, in case a spouse ventures in with the potential buyer.