Rubik101 don't be so quick to think you know everything about what you're talking about. I've had a nose wheel collapse scenario in the sim and didn't have my headrest positioned properly.
In such a scenario when the collapse occured my head was flung back initially before the nose hit the tarmac. I suffered a mild whiplash injury which took months to heal. I was not incapacitated and was able to carry out my flying duties but always had a dull ache in the back of my neck. Imagine if it was worse. Guess I got lucky.
Therefore I would conclude that headrest can be an important safety issue. I can't say for sure if it is a requirement to have headrests or not but if you have them please use them wisely.