I'm guessing you're not a parent. As the parent of a 3-year-old boy, I'd like to weigh in on this. There are three kinds of parents out there:
1) Those that simply hand their kid a phone/tablet every time they're out and about. This is probably bad.
2) Those that never let their kid use a device at a restaurant. This is pretty rare.
3) Those that use the device in times of true need: their kid has been at the dinner table for a long time and needs some distraction so the parents can get through their meal. This is where I fall, and I think it's ok. Most three year olds are not built to sit quietly and eat a meal at a restaurant. I guess maybe back in the day, people would simply leave their kid with a sitter and go out to eat, but that's not always an option.
Sounds like us. Either that or my wife and I would take turns carrying our kid around while the other finishes off their meal.
https://www.aap.org/en-us/about-the-aap/aap-press-room/pages...
Scroll down to "Among the AAP recommendations" for the tl;dr.
I am terrified by the fact that so many other people don't think twice about handing their toddler a smart device. Every time we go to dinner, there's a table nearby with a tablet planted in front of a child in a booster seat.
"There's no evidence that it's harmful", people say, but how could the evidence possibly exist? It would take 16+ years to do a thorough study (possibly longer), but smartphones have only been popular for half that time. And people have only been using them as babysitters for the past 3-5 years, at most.
We may not know the true extent of their damage until it's far too late for the affected generation. There's always a chance that the damage will be minor and/or reversible, but most people don't seem to grasp the risk they're taking.