I believe it's a mix of both.

https://en.wikipedia.org/wiki/SUV#United_States

The idea to introduce light trucks in passenger-car shape to get around pollution limits was the car manufacturers' idea. However, the US public ran with it and bought because of the perceived higher safety and social status that comes with driving a larger, heavier vehicle than everyone else. And they continue to buy to attempt to one-up each other even though the pollution limits now apply to SUVs as well as smaller passenger cars.