> It's not like they're obligated to buy a car that's so tall you can run over a child without noticing.

We're stuck in a race to the top.

Intuitively, a larger car is safer: if two differently-sized cars are in a crash, the big one will win while the small one suffers greater damage. In the modern age of safetyism, that means that if I'm on a road surrounded by larger cars, I also must by a large car in self defense. Thus, everybody keeps upping the ante, buying larger cars.

(FWIW, I don't subscribe to that approach. I favor a nimble and agile car to allow me to avoid a collision in the first place.)