can't use it to contact your daughter who's in a car with her friends
can't use your phone when you're a passenger in a car
can't use your phone when you're in a cab trying to find out directions to your mate's place
can't use in-car kits to call ahead to let people know you're runnning late
can't use it on the train to let people know when to pick you up from the station
... and it doesn't fix the problem where idiots sat at the traffic lights are too busy texting to realise that the cars ahead have moved on and the lights are changing back to red.