Orlando as I told you up thread, there are specific studies, which you are welcome to go and find, that explain the difference in distraction levels between phone calls and distractions actually in the car.
The fact that other things might also distract you does not justify mobile phone use. If anything, the reverse. If there's that much going on in your car, why add another problem? Especially one that is so recently invented.
Sat navs can and do cause problems. It's why, again, one should be careful using them and it's why people have been prosecuted for using them in cars, when it has been shown that they were not driving with due care and attention. As for screaming kids, that's why children are, or should be, taught not to distract the driver. It's why my mum used to pull over and refuse to drive if my brother and I misbehaved whilst she was driving.
Whichever way you cut it, there is no justification for using a handheld mobile in traffic, stationary or otherwise. Quite apart from anything else, it contributes to a culture that says "it's OK to multitask whilst driving" instead of one which says "driving has the potential to be dangerous, at whatever speed, and therefore I should take care whilst doing it". You can keep asking "why shouldn't I use my mobile, I'm not even moving" but the question that will keep coming back is "why the bloody hell should you?"