Fully agree that it can be distracting, but as Nigel rightly said, so is talking to a passenger, perhaps more so as you want to look at them whilst talking and nobody drives around in silence.
Does this also imply excluding the use of built in bluetooth hands free facilities that are fitted to nearly every new car now? Can't imagine how they could enforce that you cannot use a feature of the car?!
Seems they should also target people smoking in there personal cars as this also requires your hands. I know smoking is banned in company cars, but a lot of people use their personal car for work and I would like to guess many smokers chose to do so, so that they could continue to smoke whilst driving.
Talking hands free is far less distracting and talking to a passenger on your left or behind you. When talking to a person in the same room as yourself it is totally imposable not to look at them. You never look away from the road when talking on phone.
Passengers should be banned before hands free phone calls are.