Actually I have 3 children from elementary to high school age. Only my eldest has a phone. We got it for her for our convenience as she is often participating in activities with unknown end times.
Well, huge respect for raising reasonable and well behaved kids.
What makes it hard, imo, is that kids chase status and conformity (social school dynamics, probably). What could be worse than seeing everybody in class with a shiny new smartphone and not having one? Also, them being precisely engineered addiction machines doesn't really help. Which makes me curious, how did you manage to pull it off?
My daughter started asking for a phone at 9. After just saying no a few time she stopped asking. Before we got her a phone she realize why we had been saying no. Her friends that had phones younger were already addicted to them to the degree that the phone was more important than friends that were physically present. It is my job to protect my children from danger. I see device addiction to be as dangerous as drugs. Peer pressure is tough to deal with but that affects all aspect of growing up. Not just keeping up with the Jones. It takes help to navigate that feeling of missing out.
If the kid is old enough to need a phone, they're old enough to be a caddy or babysitter or something legal for kids to do and buy it themselves. You don't have to facilitate the purchase.
I think there's a strong class component to it, too.
I've got kids in public schools and one in a slightly-fancy private school.
The public school kids all get phones super-early and are prone to mocking kids for "being poor" over stupid shit like not having a phone (one of mine was so-mocked for "only having one backpack"—JFC, was Fussell ever right to shit on the class-anxious, pitiful, absurd Middle, give me "High Prole" over that crap any day).
Meanwhile, the private school kids whose parents are doctors and attorneys and VPs and related to major local politicians, get phones later and don't regard them as a status symbol. Phone ownership rate is maybe 50% by 7th grade, while I'd say it's that high (maybe higher?) by 4th or 5th in the public schools, and more like 95% by 7th. The private school also has much stricter rules about phone use during school (I gather all the area public schools have totally given up on stopping all but the most egregious use of them in class, as the parents who gave the kids the phones won't back them on enforcing anti-phone rules, and will in fact throw tantrums over any such enforcement)