That is supposition, not reality, and there are parents here who have shared their experience with kids having a healthy social life without a phone. More importantly, a very important role of parents is to make good decisions for their kids when the kids are still too immature to do that. "But all my friends are doing it" is literal child reasoning and should not be the only factor in parenting decisions.
And there are others who have shared their experiences of responsibly teaching their kids how to coexist with technology. There's probably a lot more that aren't willing to say so, because they'll be roasted in the comments for being a "bad parent".
I don't let my kids have unfettered access to social media. But I let them have a smartphone. And I took the time initially, and continually, to have conversations about having a healthy relationship with technology.
Somehow this debate is always completely lacking in any sort of middle ground or nuance.
I think it's more important to talk about the services they use than what device they're on.
And most problematic services already have an age limit. It's the parents' damn job to make sure their kids are prepared for the usage of those services.
I'm more worried about the youtube-consumption on the PC than chatting with class-mates about school-related questions via smartphone.
Never met that guy who drank every day at university or that opressed girl who fucked 50 people in the first year?
Sheltered and not parented kids end like that. Breaking the chain syndrome.