A lot of people wear their seat belts all the time,
which is good. A lot of other people do not, which
is Darwinism at its finest. (I love Darwinism!) The people who don't
wear their seat belts usually have lots of excellent
reasons for not doing so, such as:
1. "It musses my clothes."
2. "It makes me carsick." (Despite the
fact that this particular one is my wife's
favorite, I still don't get it.)
3. "The state shouldn't make me wear one if I
don't want to." (The moron's version of
civil disobedience.)
4. "What if I get in a car accident and the
car catches on fire and I can't get the seat
belt undone and I burn up?"
5. "I'm an idiot." (...wiping the drool
from their chin...)

I have investigated a great many motor vehicle
accidents during my career. I have rarely had to
unbuckle a dead person from their seat belt. In
the relatively few instances where the dead person was
still belted in, the circumstances were such that they
would have certainly died regardless of whether they
were belted in. The function of a seat belt (and
here I'm speaking as a certified traffic crash
reconstructionist so please be willing to at least
consider what I say) is to increase the ride-down time
in the event of a sudden stop. If you are on a
clear stretch of highway and you decide to go from 60
MPH to a stop, and it takes you about thirty seconds to
do so over a distance of about a mile, how hard are you
going to be thrown forward? Hardly at all, right?
Now imagine that you are on the same stretch of
highway, traveling at 60 MPH, and you come to a stop in
the span of about .003 seconds as you ram into the back
of a stalled tractor-trailer. The last thought
that goes through your pea-brain (as your brain goes
through the windshield at 60 MPH and splatters against
the back of the tractor-trailer) might very well be a
desperate wish that you had been able to slow down a bit
more gradually.
The longer it takes you to slow down, the less force
you will be subjected to. This isn't just my
opinion - the laws of physics agree with me. If
you fall backward from a standing position and land flat
on your back on a slab of concrete, it will hurt more
than if you fall backward and land on a mattress.
Why? Because even though you are still
decelerating to a stop, with the mattress it takes
longer because the mattress has more give to it than the
concrete. Everyone can agree with that, right?
The seat belts in your car have some give to them;
they will stretch a bit if you get into an accident
while wearing them. That stretching of the seat
belt if you are thrown forward or sideways increases the
time it takes you to slow down, lessening the forces
acting on your body. The stretching of the seat
belt is also the reason why I can examine your car after
an accident and figure out if you were wearing your seat
belt or not. If you are involved in an accident
and your vehicle is not totaled, you should immediately
have the seat belts replaced before you drive it again.
Once they stretch that little bit, they aren't much good
anymore.
The idea that you could be trapped in your car while
it burns up is an often-used excuse for not wearing a
seat belt. Most people rightly consider burning
alive to be one of the more horrible, painful ways of
dying, and consequently the thought that it could happen
to them if they wear their seat belt is sufficient
reason for them to remain beltless. The only
problem with that reason is it's entirely fictional.
It has never happened. For anyone reading this, I
defy you to send me a properly-researched news article
or any other information showing that someone burned to
death in a car because they couldn't unbuckle their seat
belt.
In reality, having your seat belt on exponentially
reduces your risk of being thrown around the inside of
your car during an accident, which substantially reduces
the risk of being rendered unconscious. If you
remain conscious you have a much better chance of
escaping from the car if it does start to burn, which it
probably won't. Cars rarely burn or explode in
real life - even though it happens in 99% of fender
benders in movies and television.
The bottom line is that there are no valid reasons
for not wearing your seat belt, and lots of excellent
reasons to do so. It will absolutely eliminate the
risk of being ejected from the car, and even though some
idiots seem to think that there's a possibility of being
"thrown clear" of a bad accident, in reality being
ejected almost always means winding up dead.