And, certainly not all kids would. It very much depends on the kid / the impact said ostracism would have.
It took public shaming to start to reduce addiction to cigarettes, after we were able to show how bad they were for you.
And when living in an appropriate place to raise children (playgrounds, etc near housing) it's super easy to meet other parents. And, in my experience at least, a rather large percent are also against 'digitizing' their kids.
Making friends the old fashioned way, and not just for your children.
I have a child around this age and can absolutely see the issue, but I think it's less about phones per se and more about messaging apps and/or social media. For us, banning the phone itself wouldn't have these effects because we impose suitable restrictions on use as well as having put effort into educating our kids on healthy behaviours.
There are a small number of kids in the year group with "nokias" (non-smart phones) and they aren't looked down on or deliberately excluded by others, but they might feel they are missing out on something. As the kids get older and more independent their needs for communication tools will surely grow, but not so much social media.
It's crazy there's people here defending these companies.
In other words - I'll ensure my chlidren have a small group of kids to regularly play with, ideally in the same neighborhood. Who cares what the other kids are doing?
Ah, so this yet another aspect of health that one needs a certain amount of money to enjoy.