I'm willing to trust people to be able to make their own choices. Some people find it easier to make friends than others; some of us can't always rely on strangers to even tolerate us, for various reasons. I'm a lot happier with communications technology than without it, and I wouldn't rob people of the ability to make a choice even if many of them choose wrong.
It's not just an issue for cities. One of my best friends is a high school teacher, and she said that kids told her they felt less lonely after a cell phone ban came in to effect. Before the ban kids would text their friends who weren't there if they didn't know anybody. After the ban they started making new friends at lunch, since they wouldn't choose a convenient spot and stare at their phone the entire time.
It's not like the city is a new construct.