Every state has had such laws since long before cell phones. The driver is expected to be alert, pay attention to traffic and maintain control of their vehicle at all times. Distractions can be eating, sipping coffee, women applying makeup, parent yelling at the kids, pet jumping in your lap and so on. I was opposed to specific cell phone laws simply because driver inattention was already covered.
You left out a few. I once saw a woman balancing a bowl of cereal on the tips of her fingers while driving down the highway... and have also seen people reading newspapers while they're driving. One day while driving down the interstate a woman passed me and gave me a big smile as she went by... there was also a Mich Light bottle in the passenger side cup holder, but nobody in that seat. You can draw your own conclusions which will likely be as accurate as mine.
I will admit that some people are much more talented than I am so prefer to worry about my own driving. I have never been big on talking and driving anyways because cell service is so crappy; my biggest thing was training myself to leave the freakin' radio alone.