I think it has a lot to do with the fact that food, water, and warmth are all time sensitive. If you don't acquire them within a certain amount of time, you die. Since they are all in short supply compared to chernarus, they take priority over guns and vehicles because they are not time sensitive or necessary for survival. deadlines create urgency, and urgency leads to suspenseful game play. suspense is a good thing in any game, but even more so in day z than most other titles. At any rate this thread makes me want to try the map badly.