“i've never understood adding links that require a subscription”
One common explanation is that the original author could access the link and so put it in their post. But maybe he had access for one of many different reasons. Often sites allow guest access or perhaps he had an account on the site. Or he lived in a certain area or had recently cleared his cookies or whatever. Do you really expect an author to test all the possible permutations to make sure of your access? It’s a big world out there and we assume you are a grown up who can navigate through it.