My girls had carseats before they came home from the hospital. I don't remember if the state required them in the mid-70's, but *I* did! My inlaws thought I was just being picky, and it was terrible that I strapped my babies in like that. Their babies were always perfectly safe in someone's arms, their toddlers free range all over the car. When they wanted to take them somewhere and tried to pull "my car, my rules, no carseat" I put my foot down and said "MY kids. No carseat, no rides in Grandma's car." So they didn't go anywhere in Grandma's car, not until they were old enough to use regular seatbelts.
And as for the kids being safe in the car, or that absolute nonsense about being "thrown clear" -- SonIL #1 was about 3 when his mother had an accident. He had been standing on the front seat, facing the back, and went through the windshield. He almost died. Fractured skull, brain damage that lead to significant vision problems that still affect him, 40 years later; he's gradually lost color vision, to the point that now he can see as colors only certain shades of dark blue. Everything else is like a black-and-white movie. Bright colored patterns give him headaches, because his eyes can still see the colors, but his brain cannot interpret them. He can't 'see' 3-D movies, because that requires the contrasting color vision.