> What is the advantage to those organizations to have their work preserved?

It becomes a research resource. It also creates a high-friction interface for potential subscribers.

I wound up subscribing to Le Monde Diplo because of a HN comment referencing a paywalled article. I didn't want to sign up just for one article. So I bypassed using one of the circumvention sites (I think outline was popular then). The article was compelling enough that I signed up for the paper, and remain subscribed to this day.