Seatbelts in cars were "options" that you paid for but had no choice to take them
Not in this country - once seatbelts became mandatory, there was no additional option cost to the customer for them. Of course, the cost will be built into the base cost of the vehicle but that's another thing.
 The UK - seat belt anchorage points were mandatory in 1965 and front seat belts themselves were mandatory in 1972 (although mandatory use didn't happen until 1983. Rear seat belts had to be fitted from 1986 and mandatory to use from 1991. However, the olny time I recall ever not using a seat-belt in the front of the car was the early 1970s - my parents refused to let us be in the car (certainly in the front seat when rear belts were not fitted) unless we wore a seat belt.
 My wifes' Morris Minor, being made in 1966, would have had the old-style fixed seat belts and was later retro-fitted with proper inertia-reel seat belts. But, if a car didn't have them fitted when new, you are not required to fit them later - much like indicators.