Well, I think I can mention some ideas.

Most of my social typing/messaging was with Windows Live Messenger so if I wanted to talk with somebody (or they with me) we would need to be connected at certain times, unlike nowadays when we are always "available" so in a nutshell, FOMO was a big player here.

Also I spent lots of hours in certain forums, my favorite was espalNDS, a forum that was mostly focused in sharing links for Nintendo DS games (yeah piracy was widely open before, nowadays people make it seem like a taboo lol), but as with many other communities users stayed because, well the community, the discussion, the sharing (threads), many years ago it was shut down because of piracy reasons (also the closure of Megaupload affected these sites a lot), and even some of the admins of the site were imprisoned... For a moment at least.

I also stayed in more forums, but that one was the most prominent for me.

Then the evolution for me, and many others was the social media, RSS feeds, then Reddit and nowadays Lemmy.

I still think I spend too much time on the web, but most of that time is not with a computer but my mobile.