It... kinda doesn't matter? If you're stepping out into a street, not at a crosswalk, not looking where you're going, with your face buried in your phone, you're not only an idiot, you're being incredibly self-centered.
Obviously a driver should be paying attention in that situation, and if they still hit the person, unless it was impossible to stop in time, they should be held responsible. But that's not really the point. Someone just got hurt or died, and it was completely avoidable if the pedestrian had taken some very basic steps to be aware of their surroundings.