My theory is that age verification is just another way to push human verification. These large tech companies need a way to verify a user is a real person and not an AI bot. Both for displaying ads to real users and cutting down on spam.
Nobody would support a "give away my anonymity online so I can be shown an ad for Coca Cola" bill. But it's easier to sell a law to boomers and lawmakers if you use the disguise of "It's for the children ." As if any of these companies care about the well being of children. See Meta confirming their platforms affect the mental health of children and doing nothing about it. Also platforms like TikTok and YouTube optimizing their algorithms for stealing user's attention spans.
many platform companies probably do not want to verify that a user is real, except in certain niche cases, as bots help them pump their numbers.
The ad companies I think would want the opposite
If they cannot distinguish real people from bots they can just charge more for more ads shown !
Indeed a lot of social media platforms are used by foreign powers to create discord. Human psychology is much more attentive to negative messages and this is too easy to weaponize. A solution against that would probably be world changing. It would have to preserve anonymity still of course.
That's why recaptcha is now doing human verification via mobile phone QR scan