It gave examples of how shelling didn't occur during wartime, and how latrines and food trains weren't targeted, because people wanted food, wanted to eat in peace, and need to take a crap - and if they did it then the other side would respond in kind.
I guess I'm confused about how "everybody wanted a break from it" isn't a pragmatic reason.
But the essay continues: "Initially, this was a purely instrumental impulse, self-serving cooperation to prevent retaliation." (I think that's your 'purely pragmatic'.) Followed by:
> With time, however, this sense of responsibility developed a moral tinge, tapping into the soldiers’ resistance to betraying those who dealt honorably with them. It occurred to them that: The other side didn’t want dinner disturbed any more than we do; they also don’t want to fight in rainstorms; they also have to deal with brass from headquarters who screw up everything. A creeping sense of camaraderie emerged.
I can't help but think that the essay takes on your point whole-heartedly, and doesn't ignore it.