And...I'm not quite sure that's what his attitude was. If you get to know others, and come to care about them, then they die, you stop trying to get to know them. It's not "they don't matter" but rather "I ached with the memory of people I got to know after they died, so I'll prevent more aches by not getting to know anyone else". Maybe it's easier to have zero memories than have painful memories. Regardless, many military members feel...supported by knowing someone back home will have painful memories from missing them when they're gone.