When you first start art classes you strive for uniformity. You want predictable, regular shapes.
The human (and most mammals) value symmetry as a form of attractiveness. Therefore right and left side mostly appear to mirror each other. Nature goes along with this, satisfying the consumer.
But nature is no fan of symmetry. Look under the hood and the right and left sides of mammals do different things, especially the brain.
At the upper ends of art, asymmetry, subtle or blatant, rules the compositions. Without slight differences all you have is boring drech a 3D printer could churn out with a mediocre pogram.