We can (and should) enforce fining texting while driving, that's reckless behavior that can be easily detected. It would be very difficult to be able to determine any time somebody has a phone in the car at all, and it'd be a waste of resources to go after somebody just for having it nearby. Stick to the actual dangers, texting or giving up one hand on the wheel holding the phone to your ear. Those can be enforced.
No. Telling people that they are not allowed to use their phones in their car, is not a practical law. People would end up receiving an important call while in their vehicle, and would decide to break the law based on that premise. Making advanced hands free technology a requirement in all vehicles in a much more practical way to ensure the safety of people while they talk and drive.