The mundane explanation is just safety regulations. If you want to survive a side impact, you need a thicker and taller door. Then you want side curtain airbags to deploy from the pillars, so those have to be thicker and they can't be as tall. That makes all cars heavier so you have to increase the thickness of everything, and it just snowballs.
The mundane explanation is just safety regulations. If you want to survive a side impact, you need a thicker and taller door. Then you want side curtain airbags to deploy from the pillars, so those have to be thicker and they can't be as tall. That makes all cars heavier so you have to increase the thickness of everything, and it just snowballs.