It takes a village to raise children. While it is the parent's responsibility to raise a child, it's not unreasonable for them to ask government to make society conducive for raising and protecting the next generation. The incentives are mismatched. The organizations providing access to pornography have no incentive to limit access to their product without legal enforcement.

Hacker News is filled with technical people. However, think about all the workers who are not tech workers who have families. The burden of knowledge for these parents to setup home networks and devices that provide content filtering, monitoring, and alerting is way too high.

Access to pornography ends up being an economic negative externality caused by the increased access to the internet, and we haven't really figured out how to handle the cost.