Probably because a significant portion of HN readership already subscribes to the websites that commonly make it to the front page, and others know how to bypass the pay wall (i.e. https://archive.is/lk15F if you want to read this without a subscription).
I can't remember seeing any pay walled article on HN that wasn't bypassable using popular free services online. Usually, someone will also link one of the bypass websites pretty soon after a post starts gaining traction.
I can't remember seeing any pay walled article on HN that wasn't bypassable using popular free services online. Usually, someone will also link one of the bypass websites pretty soon after a post starts gaining traction.