Some people are incapable of paying full time and attention when driving, with no other distractions. (You know who you are.) For others, it's no problem to multi-task with several things going on. It depends on the person, not the task.
Huh? Were you talking to me? I wasn't paying attention.
Cell phones?
I've seen drivers go by me in the left lane of the Interstate reading a novel propped on top of the steering wheel.