The social pressure starts around 9 and just gets worse. I just don't care if "everybody else has one". But to the kids its really important to "fit in". Up to you to teach them that keeping up with the Jones' kids isn't necessary. I feel it has been good for my kids to not have phones until teens when they might legitimately need one. Once my we got a phone for my daughter it came with a dose of lecturing about data collection and the permanence of posting anything online.
It isn't just pressure to fit in, it will mark them as different and may lead to ostracism or being targeted for bullying. In the past this was rare and kids were more understanding of friends who didn't have access but it seems to be getting worse each year.
