Repost bots (which repost contents from other sites) might be to blame for a lot of this. Or the fact that, because there are loads of (for example) World News communities, people will post the same links on multiple communities, but most people will only comment on one of the submissions. Which pushes the link-to-comment ratio up.
Beyond that, it really depends on the community I think. I see far more of that when browsing All than when browsing Subscribed.
Coffee, particularly espresso.