You might as well say

"While obviously people use HackerNews, I just don't get it. Had a account and deleted it years ago. What does it add? I see no value in it."

The same reason anyone does anything social. To discuss with friends and others topics of mutual interest, to find out about things that have happened to people and orgsnisations I care about. And sometimes to get validation by publicising things relevant to you personally and seeing the reaction.

Quite why HN seems to have such a collective hatred of Facebook specifically, far above all other organisations running social/content sharing platforms I don't understand. It's worse than /. and MS back in the day.

It's a link to people I know from real life, by their real names. Family and friends. People I have some level of emotional connection to such that I have some level of interest in seeing pictures of what they do in their leisure time, how their kids are growing up and so on. Staying in touch with them by the many other forms of communication available would be such a pain, just because there are so many.

I've spent a lot of time on pseudonymous online communities - slashdot, reddit, hacker news and others - and although there is always interesting discussion, I don't feel anything like the same interest in other posters as I do in say my housemate from 2003-2005.

Don't get me wrong, Facebook-the-company and Facebook-the-algorithmically-generated-feed are fairly vile, but the USP, the network effect is something that has emotional worth to a lot of people.

Facebook is in the ad business. If you pay, you can post ads. Its "free tier" gives the ability to exchange your time and personal network into visibility.

You get a windowed snapshot of the happiness in people's lives when you look at FB.