What is the point of protecting your head when your legs will be smashed
Maybe because that's where your brain is.
Nikolai: you've understood the brace position, I hope you're never in a situation where you have to use it. If you're tall, your knees touch the seat in front of you no matter what you do. I'm by no means taller than average joe, but found my knees uncomfortably touching the seat in front when I recently flew Tiger Airways, and so I sympathise, especially when I fly to Amsterdam where the average pax is well over 6 foot.