Good question. I’m in agreement that a cell phone is a major distraction to paying attention to traffic. Many jurisdictions now fine cell phone use while driving.
I carry my phone in the car and leave it turned on. I don’t make calls or text while driving. If I get a call, I let it ring when I’m in traffic, but answer it when on the open road with little or no traffic.
The average driver cannot concentrate sufficiently on traffic while talking on the phone, even a hands-free model.