I would not be here if I didn't get my start in my early teen years.
A smart phone is too disconnected of a device when compared to the desktops we all grew up on. No one is talking about fully banning <18s from the internet (at least no one serious) - it's a discussion about making sure that the way folks <18 use the internet is reasonably safe and that parents can make sure their children aren't being exposed to undue harm. That's quite difficult to do with a fully enabled smart phone.
By 16 I was regularly ignoring my parents to go to bed when I was up coding or gaming and doing dumb script kiddie stuff on IRC.
I had an adult introduce me to Astalavista (https://en.wikipedia.org/wiki/Astalavista.box.sk)
Thinking back to that I was very well aware of the fucked up part of the internet much more so than most adults around me. People did in fact meet up in person with strangers from the internet even back then.
I think it's more important to teach around age 10-14 about the dark side of the internet so that late teens can know how to stay safe. Rather than simply throwing them into the reality of it unprepared as "adults".
Also frankly I don't want to know the search history of a late teen. There's a degree of privacy everyone is entitled to.
It's also important to acknowledge that kids that used the internet weren't everyone in our day and the usage of the internet varied wildly. While now-a-days it's an expectation for everyone to be at least moderately online (often required by academia) and often that their presences are tied to their real names.
It's not the porn or the LiveLeak gore content that would have me worried. It's groomers and other adults with bad intentions. Not something you can easily block and not something this ID check will stop. A groomer will slow burn a social relationship with someone until they are legal adults. That's something you can only teach someone to look out for. And even adults are susceptible to this.
