I take it you don't remember the old internets chatrooms, that's why Discord is popular. It scratches a very specific itch, Live Chat. Social Media scratches a very similar itch, but with a platform that is forum based, not chat based.
Throw in the old Social Media, like ICQ, MSN Messenger, AOL Messenger, etc. and you begin to see that live chat is absolutely a feature that people want. Sometimes they want a "room" where a bunch of like minded people are, sometimes they want to talk to specific people.
Social Media as a concept has gone through a lot of iterations.