Women are social creatures. Many women will pay more attention to the people riding in the car with them, the radio, or the phone than what is going on outside the car.
Men tend to ignore what's going on inside the car and pay more attention to what's going on in traffic around them. I believe it's just that our brains are wired differently. When I'm driving, I may be somewhere in heavy traffic that requires 100% of my attention, and my wife won't understand why I'm not listening to her. When she's driving, it's just the opposite.
