Or realize that there is no way to know who is using a device without looking at the device holders for all the time they use the device. It's like ordering alcoholics or cigarettes: the seller looks at you see the white hairs (OK) or see a 16yo face (documents please.) A device registered to an adult can be used by a child. I know, it's a failure of parental control, but how many teenagers managed to get adult magazines in the last 100 years? They will get adult devices too. So there is no way to create a 100% effective system. Kids and teenagers will find workarounds, everybody else will live a worse life.
1990s: ~%36 of all teens smoked
2020s: >%2 of all teens smoke
Kinda suggests that putting limitations in place actually produces results. Crazy innit?
It also means we don't need identity verification. Anonymous scratch-off cards sold in stores to adults, just like cigarettes, can be used to verify age. Or alternatively, device-only attestation. There's no reason to verify age upon every use of the product; only when it's sold.
They all use Zyn now.
This logic is sus. Just because we cannot have a oerfect system doesn't mean we shouldn't have it at all. Like alcohol age limitations, they can be worked around and wont ever be 100 percent perfect but I see regularly teens bouncing off the register at my local store.
So the metric should be case by case for each proposed solution. Most of things proposed are no good, but that doesn't mean there is not a sensible solution out there to limit net for teens.