Arguably even HN despite being technically a pro-bono side project serves the commercial interest of YC (and possibly others) if it didn’t and especially if it would have a negative impact on them it wouldn’t be around.
And HN is a very niche social media (if you can even call it that) with strict rules.
Anything with wider appeal has to be monetized.
The only monetization we have for the Internet is attention/value extraction from the user base.