Because the internet exists outside of the US and you can get to foreign sites on the Internet?
Do we tell US companies they can’t buy advertising on foreign sites and that those foreign sites can’t be accesed from the US?
We have an existence proof of what happens when a government tries to restrict what people can see on the internet. I live in one of the states that require porn sites to validate ID. If you add all of the sites that ignored the law completely and all of the sites that you can access via a VPN, the number you get is 100%