I was wondering the same and once when I asked someone who knows about the topic the answer was basically: Don't want to give free backlinks for SEO, don't want

I was wondering the same and once when I asked someone who knows about the topic the answer was basically: Don't want to give free backlinks for SEO, don't want people to just scroll to the link and leave the site. It might just be a policy to not add links except if it's to articles on the same site, which is obviously stupid from the user's point of view.