I think car companies show off their high tech cars at CES and other electronics shows because a lot of people who are car fans and non-car fans go to CES, and read about CES on tech blogs, local newspapers, and the TV news. A lot of people who are not as interested in cars as a hobby will still buy cars to use to drive to work, and other places. They may more likely buy a high tech car they saw at CES or read about on a news article about car tech at CES. Some car fans may also more likely bought a car which they saw at CES if they are more interested in high tech features like touchscreens PC in cars, and self-driving features like auto-braking in cars. I also feel not as many people go to car shows, or read about car shows these days compared to CES and other big electronics shows. Some car companies may feel displaying their high tech cars at CES will cause more people to buy their high tech cars.