This is definitely not just boredom or background noise TV. It seems that more and more frequently people are unable to maintain singular uninterrupted focus or attention on something without staring at phones or laptops.
I actually started to pay attention to this because it started to get on my nerves when people in cinemas were doing it, and it even seems to happen more and more in actual in-person conversations. The next time you go to a coffee shop or a bar pay attention to how often people in discussions with each other go for their phone and interrupt each other. It's pretty sobering.
Personally I had an epiphany about this years ago when I started checking mail and Reddit when I was sitting down to read fiction and I was so embarrassed because I was less able to read than my teenage self when I could sit down and read for a whole day, and I just felt like the fat people in Wall-E.
This. The internet (and thus phones) has matured into a platform for behavioral addiction. Even if we want what's on the main screen, our brains need to interface with the second screen with an alarming degree of regularity.