My ears are too close to my brain

You know how people say drivers shouldn't talk on cell phones because they become too distracted? This is so true for me.

But why is that? I can talk to passengers in my car without getting too distracted. I can listen to the radio and I don't get too distracted.

So why is it that I can't talk and/or listen on a cell phone without completely forgetting that I'm driving a vehicle?

While driving home today I realized this (before I wreaked any havoc) and quickly put the phone away.