After a few days, they are typically too hungry and their energy is too low to do anything. As Jared pointed out, the biggest lesson seems to be that primitive fire lighting is very difficult under real conditions.[/QUOTE]
It's maybe not very obvious that those that have routinely trained their body systems to go hungry for a 3, 4, 5 days stretch will still have some energy to function with vital tasks such as setting up signal fires and collecting 5 X as much firewood as they THINK they are going to need to get them through the night. Those that have not, are likely to have nothing left when it comes to persevering with friction fire.
I can believe survivorman when he has to make fire in real non set up conditions and it takes far longer than he was hoping. Don't know quite what to believe when it just seems to happen on camera asif by magic.