It has nothing to do with the phones, or the use of headsets. There are a good percentage of people who can't talk and drive at the same time.
How many times have you been in a car with a driver who can't carry on a conversation without taking his/her eyes off the road, and turning their head to face you--while you sit there grabbing the edges of your seat as you close in on the car ahead of you?
When I was about 30 years younger, I was with someone who ran a cyclist into the weeds trying to light his pipe
