They are reliable, safe, affordable in the case of Toyota, and effortless transportation. Buyers seem to be people who really wouldn't rather bother driving but hey, we live in America, so you can't get by without a car.
This contrasts with, say, Honda drivers. They also wanted reliable, safe, affordable cars. But they enjoy driving.
I say this as a person who's driven Audis and BMWs, known dickhead cars.