How do you reconcile porn sites as a line in the sand with things like banking or online real estate transactions or applying for an apartment already performing ID checks? The verification infrastructure is already in place. It's mundane. In fact the apartment one is probably more offensive because they'll likely make you do their online thing even if you could just walk in and show ID.
I mean, we're talking about age verification in the OS itself in some of these laws, so tell me how it doesn't.
Quantity is a quality. We're not just seeing it for porn, it's moving to social media in general. Politicians are already talking about it for all sites that allow posts, that would include this site.
So you tell me.
California is also stupid for creating liability for service/app providers that don't even deal in age restricted apps, like calculators or maps. It's playing right into the "this affects the whole Internet/all of computing" narrative when in fact it's really a small set of businesses that are causing issues and should be subject to regulation.
There is also the problem of mission creep. Once the infrastructure is in place, to control access to age-restricted content, other services might become out of reach. In particular, anonymous usage of online forums might no longer be possible.
OS-level ability to verify the age of the person using it absolutely provides infrastructure for the OS to verify all sorts of other things. Citizenship, identity, you name it. When it's at the OS level there's no way to do anything privately on that machine ever again.