When I was a kid, in the 1970s, our car didn't yet have seat belts in the back, but in the front, they were required. I think when they became required in the back, it also became required to use if you had them, which obviously older cars didn't.
But having seat belts for decades and then not expecting people to use them, that's kinda silly.
I think "not expecting people to use them" is in accordance with actual facts, a substantial portion of drivers would flat-out refuse to wear seatbelts. (I feel as if this has changed in recent years, as those people age out, mellow, see reason, or die in car wrecks).
But having seat belts for decades and then not expecting people to use them, that's kinda silly.