Well technically, unlike Spartan-II's, Spartan-III's were trained and designed to have a lower life expectancy than II's, they're basically mass produced Master Chiefs.
I do feel that they were trying to show that horrors of war thing, I just think they didn't do a very good job; kind of like how Epic tried to convey emotion by showing the scene with Dom finding his wife in Gears of War 2. It was technically a sad scene that you should be able to sympathize with Dom about, but.... c'mon, no one really felt bad after watching that.