As I said I don't have to watch it, just hearing the lines is a gas. Even if it were playing with the screen off, the sound track and dialog of that film is so great I would be fine with just hearing it.
You are right though, there are things you could be doing on a car that it would be distracting from creating something. But some of it like simply blocking out a body for instance something like that playing wouldn't get in the way of anything.
Hell, I often get side tracked when one of my old albums are playing on the turn table too. Love that music!