Pictures like these seem to indicate that not wanting to interact with other people while using public transportation is a timeless phenomenon. After all, even the slightest eye contact with a stranger can lead to minutes upon minutes of awkwardness. Is being absorbed in personal entertainment a bad thing in this situation?
What I've noticed in my increasing usage of MARTA trains and buses is that there is a third option: the aware stare. The passenger sits casually, with no book, phone, or other diversion, simply staring at one point after another. When two people are doing the aware stare, the trick is to turn the head, glancing at the other person, then looking just over their shoulder. The message sent here is simple: "I'm on the bus, and you're also on the bus, and that's a thing that's happening." You show respect to fellow passengers by acknowledging their existence, but not assuming that they want to interact in any way. I look forward to the day when I can sit in a bus full of starers in complete, but very aware, silence.