I suspect (based on a loose study of my family), us older generation believes that the more important people to focus your attention on are the ones in your presence (at the table, in a meeting, etc) and that the person on the other end of the line can wait.
Our kids however, feel that certain people are more important than others regardless of where they are. Their friends are more important than any boss or family that is nearby.
And so, my wife and I will let the phone ring / answer machine take the call, ignore text messages / FB notifications, etc during supper.
And my kids are squirming as if in extreme pain if their phone buzzes and we don't let them immediately see who it's from and if it's a friend let them respond.
I'm not going to say it's a bad priority shift, but it certainly is an interesting one.