I know it's a feel good story and all to bash Capitalist car manufacturers and all, and there are probably some examples where what you're saying is true, but GM seatbelts are pretty standard across all models and get small updates about once a decade. Defects are very rare in this area. Notice that when stuff gets recalled, it's usually recalled against many models over a number of years... That's not the hallmark of things getting updated just for the sake of it. It's also inevitably expensive for the manufacturer to create new parts where none is needed and existing parts are already in the parts bin.
Important stuff generally gets updated when new functionality is needed (like ignition disabling circuitry to make cars harder to steal). It's not like there's a group of Engineers sitting around thinking of ways to redesign basic things that work. They won't win new customers by redesigning seat-belts and ignition switches.