The point of this quotation is that a cell phone is a very personal thing. It's anxiety inducing and burdensome to hand over your cellphone to someone.

And that's not the mention the power dynamic between the kids with the cellphone and the kid without.

This kind of independence might be a social plus for a kid. Something like "I don't need a phone cos I can go where I want until dinnertime". No helicopter parenting.

Assuming neither, they're probably getting picked up and dropped off by a parent or other family member, with dropoff/pickup schedules arranged in advance.

It's less, "I don't need a phone cos I can go where I want until dinnertime," and more, "My mom will be driving 25 minutes to pick me up at 4PM, and my friends spontaneously decided to go bowling. I can only ask her when she gets here, but that would mean she needs to drive another hour and fifteen minutes."