There's no real difference in that situation, but people don't generally read paperback books when out to dinner with friends, while driving on the highway, while walking on a crowded sidewalk, during a movie at the theater, during class at school or in a meeting at work... which are all common situations where I regularly see people glued to their phones.
I wasn't necessarily implying that what people are doing on their phones in those various situations is a waste of time, but trying to showcase the sheer distractive power of smartphones vs traditional media.
