AFAIK The birth birthday itself is not "required by law" but there are several restrictions for services directed to children under 13. I can think of the most

AFAIK The birth birthday itself is not "required by law" but there are several restrictions for services directed to children under 13. I can think of the most known Children’s Online Privacy Protection Act (COPPA) and some EU safeguards that prevent you from processing a child's personal data without the guardian consent. I would also guess that there are content restrictions that might be hard to implement on a Google account and they prefer locking children out of their platform. I do think Facebook and many others applies the same method. Disclaimer: This is not legal advice