I make phone calls from the car quite safely all the time, WHILE SOMEONE ELSE IS DRIVING. My guess is that considerably more than 0.5% of the population can do that.
Apropos the comment that you can get distracted while talking to people who are in the car, it's true, but the difference is that since they're in the car, they can see what's going on and will generally stop talking if they see you need to pay attention and drive. The person on the other end of the phone call has no idea, whether he's on speaker or handheld.