Not that long ago, you could very quickly build a decent SEO campaign around "X vs. Y" tutorials and HN - write 5,000 words on e.g. Angular vs. Ember, get some friends to upvote it, and if you made the front page you'd be on the first Google SERP for Angular and Ember the next day.

I personally know a couple of early-ish YC companies who took advantage of that to boost their content marketing ops, and it wouldn't surprise me to learn that they were part of the reason this policy exists.