I hypothesize that the person who talks constantly on a cell phone is probably more likely than average to be the kind of individual who doesn't pay attention ever, cell phone or not.
Furthermore, what kind of a call is being made? Yes, it does matter. If a cell phone is being used in a frank business-type fashion to deal with a problem of relevant nature (such as "I just got off the freeway; I will arrive in 5 minutes.") it is certainly not as distracting as a teenager-ish call (such as "Hey, how's it going, and, like, I can't wait to tell you about..."). Also relevant; when? If it is a two lane country road, that is different than the downtown freeway interchange at rush hour while merging.
I'm boiling this down to the suggestion that if you run over a raccoon because you were talking on a phone, under different circumstances you - being the same person - might still run over the raccoon, because you would be craned around looking out the back window, or doing something else equally foolish.
The problem is not tied quite as tightly to phones as it is to irresponsable people (though it does include phones.)