On HN we're interested in the diffs [1]: what's specifically interesting about an article. Generic tangents pull threads away from that into the gravitational field of the nearest large topic, sort of like a spaceship flying too close to a black hole [2]. The generic topics are larger, more familiar, and more repetitive [3]. Familiarity is seductive, but repetition is bad for curiosity [4], and curiosity is what we're trying to optimize for [5]. The generic themes are usually more sensational and inflammatory, too, which is doubly not what we're looking for.
It's super tempting for threads to hop to the most-generic adjacent orbit. Often they make several such hops. By the time a discussion reaches "People are cruel", that's a good example of a black hole. No light is going to come out of such a thread.
[1] https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
[2] https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
[3] https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
[4] https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...
[5] https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
p.s. Not saying the generic topics aren't important in society at large. They're usually much more important than most of what's on topic here. But a site like HN needs to stick to what it's for.