Why do so few people use corpses to feign death for self-preservation in war?

There have always been many who feigned death or were on the verge of death under piles of corpses.

After the Battle of Borodino, on the morning of September 8, Heinrich von Roos, a military doctor from the "Duke Louis" Jäger Regiment (3rd Jäger Regiment) of the small South German state of Württemberg, witnessed such a scene.

As the first rays of sunlight shone on the masses of the living and the dead, I found myself at the top of the Redoubt, captured by the Italian Army [4th Corps of the Grand Army] the previous evening. I saw the Viceroy [Eugène] and several of his aides wrapped in greatcoats, warming themselves by a fire. They were using the rear part [wooden debris] of an overturned Russian cannon carriage to feed the fire. As far as I know, the Viceroy spent the night there. The Redoubt had been destroyed, and the excavated earth buried hundreds of the dead and dying wounded.

As far as the eye could see, both near and far, the camps of the troops were visible, as were the countless corpses. Among the latter, a young Russian caused a great stir. Whether it was the first rays of sunlight that revived him or the commotion around him that woke him, he suddenly emerged from the pile of bodies. He rubbed his eyes, slowly stood up, and looked around in astonishment before heading in a direction he believed to be deserted. Many noticed him, but no one attempted to stop him. It was generally believed that the most likely scenario was that this young man had been terrified by the terrible and prolonged bombardment the previous evening. Perhaps a solid shot had passed close by him, or a shell or similar projectile had caused the earth to fly up. In any case, he had fallen to the ground, appeared to be dead, and had spent the night among the corpses.

In summary, this young Russian either possessed an extraordinary ability to feign death or was genuinely incapacitated by the shelling. He spent the night buried among the layers of corpses and only revived and left the next morning under the faint rays of sunlight.