[cjbprime]

Could be because people don't generally drive 40 year old cars! The aircraft in the first fatal link above was manufactured in 1979 and the seat failed in 2016; the second was manufactured in 1969 and crashed in 2014.

And because it would be less likely fatal in the car, so you'd be less likely to hear of it happening.

(Less likely fatal because car collisions are less fatal due to e.g. airbags, and less likely to impact terrain since it only takes a second to undo your car seatbelt, and because there's no pitch control to have messed up.)