>I ask because I feel like if we don't do something, the trajectory is that ~every website and app is going to either voluntarily or compulsorily do face scans, AI behavior analysis, and ID checks for their users, and I really don't want to live in that world.

The only reason they'd _have_ to do that is government laws making them do so. When the law is vague around what age verification is, if one company decided to do ID verification, now any site that doesn't might not be doing 'enough' in the eyes of the law (it'd come down to a court case if not specifically defined).

Though it may seem more convenient to just do it at the os level (though really the browser level would make more sense with a required header/cookie no?), I'd be shocked if you don't see it expanded in the future to be more than a checkbox.