1) If you're an Aron Ralston type of person, you're probably a Darwin Awards poster child, anyway, so why drag out the inevitable?
2) For snakebite, you mainly need to get to a hospital. And where you get bitten makes a difference, too. In a vein? Bye-bye!
3) If you have a means of making fire and don't do so, waiting until you're hypothermic, see #1 above.
4) Dehydration can happen in more places than the desert. Lack of a container can be a really big issue if you find water, and then have no way to transport it. All the water is frozen? Again you would need a fire and a container.
5) Most animal predators don't like fire. Start several fires and sit in the middle, or make a couple with your back to a really big rock.
So, for the situations listed, a Altoids tin with a lighter, an oven roasting bag, and a leg of pantyhose would help you survive.
And they give you a mindset that you CAN do something to help yourself, rather than just wandering around like an idiot, crying in the wilderness.
Sue, Devil's Advocate and SideKick, 3rd Grade