That's a terrible comparison. People have to show a government ID to buy alcohol, stating your age on a website is much less of a verification. Plus, there are few kids out there who haven't had the idea to lie about being 21--it's just much more difficult than giving a different birth date to a website.
> People have to show a government ID to buy alcohol, stating your age on a website is much less of a verification.
And yet it's worth enough that it's a law that you must attempt to trick the children.
> Plus, there are few kids out there who haven't had the idea to lie about being 21
Of course not. Because it's not a secret restriction. So anyone any everyone can dream of bypassing it. And it's easy - you can get a drunk to buy booze for you anywhere.
But instead of tricking people we still say it outright. We know some will be driven to crime but it's worth it that the law-abiding get to choose their path.
Lying makes the law just an annoying obstacle to be bypassed instead of a healthy warning and in doing so starts to erode any trust its victims might have had in a just and reasonable government.