I have been recently opening accounts for my son on several websites that are asking for age. I truthfully filled in his age — I think he was 10 at the time — assuming that would optimize the service for kids. To my dismay, several websites used this information to immediately, permanently, and irrevocably block my son's account.
After that experience, I now dutifully tell all websites that my son is 18 years old and I instruct my son to do the same. The sad reality is that people under 18 have access to online services limited to such an extent that they have Internet access effectively forbidden. I say people, not children, because nobody over 15 is a child anymore.
Why do service providers, all private businesses, even do this? First reason is that children cannot independently sign legal documents and they therefore cannot accept Terms of Service nor any license agreement.
Second reason is that new laws are being passed around the world, which introduce harsh penalties for harming children on the Internet. For an online service, especially one that mediates communication between users or carries user-contributed content, it is cheaper to boot children from the service completely than to moderate content in the extreme ways required by laws. CYA.
Third reason is that children don't have their own money and it is therefore impossible to sell them anything, neither directly nor through ads. They can nag parents for money, but that's less lucrative for Internet businesses. Furthermore, there are restrictions on ads targeting kids.
Whether intentionally or not, legislation and economic system are set up to prevent children from accessing the Internet. Lawyers behind the legislation will always tell you about their good intentions, but they too must have been well informed about side effects of the legislation they were pushing through, which makes me very doubtful they had good intentions when they proceeded anyway. In my opinion, this is all about suppressing civil freedoms. If the lawyers wanted freedom for children, they would push through prohibition of unjustified age discrimination instead.
Oh, by the way, lawyers... They made a mess of the real world and now they decided to screw up the Internet too. All these new technologies are a pain in the ass for them. Automated decision systems and self-regulating communities everywhere. Where are their beloved courts, law firms, government offices, forms, permissions, state borders, and political parties? What is a poor lawyer supposed to do now? Retrain and start doing useful work?
Of course, there are websites dedicated to children, which do not restrict access by age (or even exclude adults), but those are small and so childish they are like an Intertnet version of sandbox. Would you like your child to learn programming before university? No way! Back to the sandbox with kindergardeners!
I dread these new proposals for state-issued digital identity. Lawyers and child "safety advocates" are alarmed that 11yo boys click-through "yes, I am 18" popups on porn sites. Let's ignore for the moment hypocrisy of this society, which prohibits porn before 18 years of age, which is 6-7 years past the beginning of puberty, as if porn was munition. The main threat to children is that this cryptographically secure, unfalsifiable, government-issued digital identity becomes mandatory for access to virtually every relevant website on the Internet. From children's point of view, that will be the beginning of new Dark Ages.