During the approach, sure, there's a lot going on, but it's also highly regulated. You're dividing attention between the controls and the radio, but 1) you have

During the approach, sure, there's a lot going on, but it's also highly regulated. You're dividing attention between the controls and the radio, but 1) you have another person to help you, and 2) the people you're talking to on the radio are there specifically to make sure you don't hit anyone. In IFR conditions, as you've obviously experienced yourself, paying attention to the radio is probably more important than looking out the window. In a car, on the other hand, the phone is pulling your attention away from the road, detracting from the navigation process rather than aiding it.