Comment by AnthonyMouse

People are willing to post links to paywalled articles when there are ways for people not currently inclined to subscribe to read them. Even if 97% of the current non-subscribers bypass the paywall, having 3% become subscribers is very useful, especially if they become recurring subscribers.

If posting the link instead implies that the 97% of people not currently willing to subscribe can't read it, then people instead post a link to a publication their audience can read, in which case the first publication gets actually 0%.