Panning ranges from decisive L/C/R placement to evenly spread positions, by taste
Beyond the technical reasons for central placement, stereo positioning of other parts is largely personal taste with scant regard for realism. Some engineers pan almost everything hard left, centre, or right (L/C/R) for maximum separation and openness; others dislike hard panning and spread parts evenly in pairs across the field to build width. Both are legitimate; the choice is aesthetic rather than a question of stereo realism.
Examples
One engineer keeps pans “rarely anywhere but left, centre, or right”; another pans layered vocals 40/40, 50/50, 70/70 to build width and avoid parts feeling isolated.
Assessment
Contrast L/C/R panning with even-spread panning and state which instruments stay centred regardless of approach.