Should seatbelt use be mandated by law? I would say no. As others have said, and I believe this totally, The Govt. does not care about your safety, these laws are just 'revenue generators'.
Having said this, should one voluntarily wear the seatbelt. To this I would say yes.
I never wore a seat belt, ever, and drove cars that had no forgiveness when you wrecked them, unlike the vehicles of today. I went through a windshield out onto the ground, took the steering wheel off with my chin...and then got up.
Yet I did not wear them...still.
It was not until my last child was born did I begin to wear the seatbelt, to set a good example to him(and was in custody case).
Again...having said this...I was involved in a head on wreck (12/04), pushed into oncoming traffic after being rear ended. I, as well as my son had our seat belts on, otherwise this would have been a 2 fatality wreck...the dashboard was pushed back so far that my sons cheek came to rest on it...I was entangled in the front end of the van...
Without a seatbelt, we would have been killed, without doubt. Fortunately my son only broke his nose.
I compound fractured both femurs, shattered my knees, broke 3 ribs, my left arm, and tore my foot off.
I carry a lot of Titanium, but am still alive.
And don't be fooled by unrestrained things behind you in the vehicle, people, cargo, junk, it will come forward, this is simple physics.