When I see a bunch of people sitting around together reading books, to me, that implies a closeness between those people. Conversely, when I see a bunch of people sitting around together doing stuff on their smartphones, it looks like there's a distance between them.
Despite the fact that both of these attitues involve people sitting near each other, but not paying attention to each other, I interpret the situation differently.
The most obvious explanation here is that I'm just old, and don't get the smartphone generation, or the appeal of smartphones. (What would I understand about sitting near a bunch of people you know, but staring at a screen, having low-bandwidth textual conversations with people who might be thousands of miles away, or even having those conversations with someone in the same room rather than talking to them face-to-face?)
Some people have said that spending time on your phone is different, because it signals to the people around you that you'd rather be spending time with other people than with them. I think that gets close to the reason, but it's not entirely there, because for those people reading books, aren't they signalling that they'd rather be spending time with a bunch of imaginary people that with those around them?
I think the real reason has to do with intentionality.
When people take books somewhere, it because they intend to read that specific book. That's a thought-out plan of (sedentary) action. When multiple people take books somewhere, to read together, that implies a certain level of co-ordinated planning. It implies those people have agreed that reading is something they all want to do, and they'd rather do it near each other than alone, in spite of the fact that books can be read perfectly fine alone, and doing any co-ordination is harder than doing none at all.
Whereas people take their smartphones everywhere. There's no plan there. Playing on a phone is a distraction of last resort. People play on their phones when they have literally nothing else to do. OK, that's a half-truth - people also sometimes play on their phones when they do have some other things they could be doing instead. But still, playing on your phone can be a signal that you didn't plan for the current moment, and you cannot think of a single other thing to do. So a bunch of people sitting around together, but playing on their phones, can suggest that they're only doing so because they see zero value in interacting with each other. They believe they have nothing to say to each other, and nothing to gain from listening to what they might have to say.
Of course, that's not always going to actually be the case. But it's one of the possibilities in the solution-space to the question of "What relationship do those people have to each other?" that one ponders when seeing such a group.
Do you think that's it? Is it a lack of intentionality to the action that I see creating a distance between people using their phones, that makes it different from those people reading books?
Or should I go back to my first hypothesis, and attribute my perception of a lack of intentionality to these people's actions as a result of being old?