I think lawmakers gravitate towards "required identification" because 1) it's easier to put blame on a single website than on whatever browser + the websites 2)

I think lawmakers gravitate towards "required identification" because 1) it's easier to put blame on a single website than on whatever browser + the websites 2) it matches th experience of age restriction for movies and magazines, where age is enforced by whoever sells you the thing or allows access 3) client side restrictions seem easier to circumvent 4) some lawmakers probably think grown ups shouldn't watch porn either. IMO an "ok" solution to the parents' requirements of "I want my kids to not watch disturbing things" might be to enforce domain tags (violence, sex, guns, religion, social media, drugs, gambling, whatever) and allow ISPs to set filters per paying client, so people don't have to setup filters on their own (but they can). But it's a complex topic, and IMO a simpler solution is to just not let kids alone in the internet until you trust them enough.