I do not dispute that talking or texting on a cell phone can inhibit good driving.
But laws that limit the use of cell phones while driving may still be undesirable.
First, the people who text while driving might be the same people who would otherwise be putting on makeup, fiddling with the radio, trying to eat a sandwich, or yelling at their kids. Thus, the net amount of bad driving due to cell phones may not be large.
Second, traffic fatalities per vehicle mile have declined steadily and significantly since 1994, even while cell phones and texting have grown enormously. This does not prove cell phones do not cause bad driving, but it makes you wonder if this effect is large. Most studies on cell phones and traffic accidents suffer from serious statistical flaws.
Third, any accidents caused by cell phones are only one side of the equation. Millions of people use cell phones while driving for beneficial purposes, so the net impact may well be positive.