Growing up in the 60s, we never wore seatbelts in the car and it's not like there were even airbags or a zillion other safety features that there are in modern cars.
It's easy to make fun of some of the safety obsession we see in society but the fact is that if you look at some dangerous toys list of years past, a lot of them we wouldn't have today for mostly pretty good reasons.
Was wondering if seat belt laws would be evident in the data, just eyeballing it looks like 1989-92 decreases in motor vehicle fatalities [1] could line up with the rise of state bans starting in 1984 [2].
But seeing a pretty linear decline from 1921 to 2021 and looks like big annual drops in fatalities are more connected to economic conditions than safety features (i.e. only double digit % drops I'm seeing are 1932, 1938, 1942, 1943, 1974, 1982, and 2008).
So the drop in the late 1980s into the early '90s may've had more to do with the early '90s recession.
All the other safety features. As you say, maybe differences in miles driven because of recessions/fuel price spikes. DUI/DWI becoming less socially acceptable, at least in many segments of society. The overall evolution of attitudes towards risk.
I wouldn't expect the laws themselves to have a huge effect. They mostly trailed public opinion, enforcement was limited, and penalties small if someone really didn't want to wear a seat belt.
It's easy to make fun of some of the safety obsession we see in society but the fact is that if you look at some dangerous toys list of years past, a lot of them we wouldn't have today for mostly pretty good reasons.