The funny thing about the cell phone studies is that they don't seem to explain why the rate of car accidents haven't exploded since cell phone usage became widespread. I guess the studies may be biased or otherwise designed poorly. One explanation for the results of their study could be that the subjects were asked to talk for lengths of time that do not correspond to the typical pattern.
The reason drunks get into accidents is that once they're drunk they're going to stay drunk for a while, probably the whole duration of their trip in the car. Drivers on cell phones, on the other hand, may talk for just a few minutes. So the amount of time during which they are distracted, as a percent of their total driving time, may be relatively small and may not pose as serious a threat to traffic safety as it may otherwise seem.