Also note that the people retrieving the dead in both cases are in the same group as the dead, risking their lives in the same way. They have presumably thought about the possibility that they will die in the same way, and the idea that someone will retrieve their corpse and return it to their loved ones probably brings them a great deal of comfort.

You can just chalk it up to culture, but there is also a logic to it that is every bit as logical as the "leave my meat where it falls" crowd: if you have a culture of retrieving the bodies of the fallen, no matter the difficulty, then that means that you won't leave behind the wounded to save your own skin. This, in turn, makes it easier to trust and to risk your life for your comrades -- they'll take care of you in turn, living or dead.