Only convinced immortals and believers of fairytales believe they can avoid accidents or death by reacting fast. The rest of us need to play the odds and wear a seatbelt.
Our puny little forearms will not be able to stop our forward motion when something blocks the vehicle's forward motion.
Nor will those arms be strong enough to stop the dog or infant in arms from continuing forward until they hit the dashboard (or the airbag).
As for the "I was thrown clear" when the vehicle rolled argument, or other statistically-rare exceptions to the rule... It might happen once, but what about next time?
I don't think the government should mandate seatbelts, and I hope no public funds were spent on the ad, but it's in the best interests of insurance companies to prevent head injuries, and the benefits to passengers are obvious.
If I were on a jury in a case involving the non-use of seatbelt injury, I would consider the "victim" had some responsibility, too.
What do you think? http://consequeries.com/