As someone who still consumes threads like that, it's part of the charm and beauty. None of the stuff is ranked/upvoted/liked, no one is competing to have the most followers, just conversations/arguments between humans for the sake of communication and understanding. Requires a bit more time and effort to read, true, but everyone being equal makes it feel like a pretty OK tradeoff, at least for me.
Of course, not all forums are like that, some still have vanity-metrics, but at least the forums I still participate work like that.