At least Medium's algorithm shows it to users within Medium. A personal homepage doesn't get picked up well by SEO, and unless it becomes famous, you can't see any comments from people. Just like my homepage(makonea.com) that no one visits
The original post is also available at the poster’s own blog [1], so the question is a very valid one. Clearly, “posting articles for free” is a hurdle already cleared by the author.
That is in fact a better explanation due to bringing up different reasons (zero cost to host as you mentioned, vs. network/visibility out-of-the-box in the linked comment).