In my case, I have a background in statistics and biotechnology and I use Hacker News (via RSS) to learn about new developments in machine learning and related technology. I tend to ignore all news related to politics/social issues because HN, on average, has a very narrow-minded (too engineer-like, often ignoring a lot of vital nuances) way of looking at those topics. Also, I'm from Europe and I find that there's a particularly American way of looking at business and personal projects that we don't have here and that I feel beneficial to get exposed to (even with its downsides).
Edit: To expand a little more on my process of using HN, in case anyone finds it interesting, I subscribe to the frontpage RSS feed, so that I usually get between 75-100 stories (just the headlines) per day, which I then proceed to quickly scan to open the interesting ones (both the original URL and its accompanying HN discussion). I've found the signal/noise ratio to be more than worth it (also factoring in the time it takes me to do all of this).
Stuff like...
"Oh I can tell you a thing or two about the legal complications of cubesat launches, my company did this for the last 12 years. [...]. By the way, this is our website"
...is probably more effective if a potential client stumbles over it than 100,000 "targeted" facebook ads, especially if you serve some highly technical niche.
So it does happen a fair bit if your startup is relevant.
Personally I come to HN because it’s one of the few places you can have a discussion and read comments without having to dig through dozens of memes and low attempt jokes.