Not that long ago screen time meant a TV in the living room. Gaming meant a hardwired console on that same TV, or a computer in the computer room. When you weren't at home, there was not a screen. In today's World, the screen is in your pocket wherever you go. Children know this and the temptation is hard to resist when screen time is so accessible.
Children see a large majority of adults engaged with their screens and think, if they can do it, why can't I? Next time you're on the bus or subway look around and try to find the other person doing the same. Practically everyone is looking down unaware of their surroundings. It's the World we live in today and our children are following our lead. Parents need to do their best to set an example.
Although it's science fiction, the second book from the "Three Body Problem" series by Cixin Liu offers an intriguing idea he labels as the "Dark Forest". The gist is that the primary motivation for all civilizations is survival and other civilizations are a threat. This Quora answer gives more detail, but I highly recommend reading the books; there are many compelling science-based ideas within it.
This is a prime example of how people so easily accept a headline shared on some news authority to be truth. Even the bright minds at hacker news are duped - just look at all the discussion happening here with the assumption the headline is correct.
The guy who tweeted this jumped to a conclusion, naively shared his discovery, then let it perpetuate leaving numerous victims of an erroneously altered world-view.
You're missing the "herd effect". There are cases where children are too young or have another health issue that prevents them from being vaccinated. These children rely on the greater population to be vaccinated and to help decrease their chances of becoming infected.