Many online newssites make most articles available for free.
This is due to an idealistic approach to both journalism and the web, aiming at keeping news available at low costs for everybody.
The reason for this can be seen in an overly long peroid of experimenting: The possibilities the web offers are still being explored with the aim to develop a sucessfull business-model, testing audience reactions, click-flows, paywalls, content-types and the like. Since that has cost more than it yielded for too long for many companies and did not generate a sustainable business modell, the digital transformation of journalism is at least in part a failure.
The news sites would not do this unless they had figured out an alternative way of bringing in revenue, such as advertising.