We did usability tests with drivers, so we already know what works
And we don't waste time on something that doesn't. Knowledge is vital for automotive projects. Knowledge allows us to avoid mistakes that could result in safety threats for the future users of your products.
We've accumulated this knowledge in many ways: we've designed many application screens, we've driven many miles in various types of cars, we've explored users' behaviour inside and outside of the car. In other words, we know what to do.