Well, you hit the nail on the head when you said primitive cultures. With the invention of portable stoves, ultralight pack saws and all our other modern gear we don't have to rely on these skills and tools like primative cultures do. I would venture most primative cultures know more about real survival than most of us will ever know(or would like to know) Especially when most of us only venture out into the "wild" for a few days at a time before returning home to our warm houses.

If I was trapped on a deserted island for a couple of years a big knife is exactly what I would wish for. A large knife can do everything a small knife can but usually not the other way around. For a weekend out or a short term survival situation most of us could get by with a very modest sized knife.