Although what you saw could have been coincidence—maybe something urgent had come up and they were all looking online for a solution—, I have to say I usually react just as you have. What strikes me as a sadder sight are couples doing that or, even worse, groups of friends, especially adolescents. They say that familiarity breeds contempt, and that kind of thing might be understandable in a family who've spent the last few days together on a trip, for example. It seems to be less and less reasonable as the bond among the individuals goes from blood to friendship.
Yesterday morning, I took my computer to a technician across town for some routine maintenance. I went there on my bike, with the computer in a backpack. There was a narrow bike lane most of the way, built between the road and the sidewalk, and I crossed paths with another cyclist going in the opposite direction in the middle of a particularly sharp S curve. As you might have guessed where my post is going, he didn't look up from his phone through the entire maneuver.
Editing because I forgot to add that I was top-heavy because it's a desktop computer, not a laptop. And the temperature was near 100 °F yesterday. It was enough to see red, as they say, but I was too exhausted to even think about it until this morning.