Well, I do eat on a long drive. I'll have everything arranged ahead of time to make sure I can do it all one-handed without taking my eyes off the road.
And NO, eating a sandwhich while driving is not the same thing as talking on a cell phone as I am not using any significant number of brain cycles compared to an active conversation asking/answering questions all while holding a handset by your ear.
90% of the time I only have one (left) hand on the steering wheel (an old habit of driving manuals around town where the right hand is pretty much glued to the shifter) so it makes little difference whether I am shifting into another gear or grabbing a chip from the bag. In both cases my hand can find it without thinking about it.
When a chunk of food falls off onto the seat, I just say "fack it, I'll clean it up when I get there"