We have some casual acquaintance we visited two or three times. Their then-4yo was constantly on an iPad on YouTube Kids, switching videos every 20 seconds. Just watching him was infuriating. You had rather innocent or mundane videos of e.g. model trains driving around, but before you could start to pay attention to any details or any kind of narrative, he'd switch to a video of kids in a swimming pool full of orbeez, then something Sesame-street-like. And they just let him keep doing that since he'd throw a tantrum if they take away the iPad. They have to let him watch that stuff at the table, otherwise he wouldn't eat. Fast forward to last year, he got into elementary school and was absolutely unable to pay attention to anything. Teachers made him see doctors, he's on medication now, but that was half a year ago so no idea how things are going today.

Now I'm sure someone will pull the "are we sure we got cause and effect right here?" card, but even if that kid had some kind of predisposition, nobody can tell me that just putting up with the kid's tantrums when he was still four (or whatever age he started at, this was just when I first saw this) and taking away the iPad, going outside more would not have significantly improved the outcome here.