I think they are looking at the concetration factor, how you can get caught up in a converstation on the phone and get distracted from paying attention to your driving. Sure one can argue that passengers can do this also, but it makes you stop and think how long till they ban p-platers from having passengers totally.
I don't agree with this law totally, I think if you are going to be that radical thewn ban everything that involves taking your hands off the wheel unless it is to change gears, indicate or put your wipers and lights on.
Eating, smoking and drinking should be banned if they are going to go down this line. At least with a hands free you can keep both hands on the wheel. Try driving and eating a hamburger, steering with your knees! (Note for those with no sense of humour, like the head job joke before, I don't condone nor partake of this sort of behaviour in a car.)
