My point is that if we make adults sites harder for adults to access, many people will turn to the unregulated black market, which is much worse. It's much closer than people think: once VPNs are banned or restricted, the next easiest circumvention solution is Tor. We don't need age verification per-site when we have client-side parental controls, which are widely trusted by parents.

Gambling is a system which inherently requires payment, for which it is easy to request a credit card as proof of age. It's also necessary to create an account to track your winnings. For adult content, the main business model is the free ad-supported system with account registration optional. ID verification systems charge about thirty cents per user, which takes a lot of ad views to recoup, so to avoid verification cost on every visit the user must create an account (which is subject to account sharing anyway, and as the article notes, verified accounts are being sold on the black market). Parental controls client-side make much more sense unless your actual goal is to harm the adult industry and increase government surveillance of citizens.