The problem with many of these skills is that they take a lot of time... often that time would be better spent getting out. Even in very remote wildernesses you are rarely more than a day or two hike from civilization. It takes a month to die from starvation. Giardia takes weeks to develop. Keeping moving keeps you warm. Lighting a fire when you are cold and wet and don't have matches or a lighter is a real challenge. That is when you need a fire and you won't have the time or energy to make one. Spend that time getting out.