It's a decent point, but you didn't follow through. The whole point is that cars depend on computers MORE than having a computerized dashboard. What you are mentioning in your second paragraph is quite trivial.
Computers are used to regulate just about every system in your car. If a "hacker" gets into your car and shuts down the brake system then it's a whole lot worse than if he's just putting a picture of Goat.se on the dashboard.