Search engine exposure. For technical topics (cars, computers, whatever), information topics (example: such as discussing a TV show, book, music band or film)...
Twitter and Reddit are often pretty good at getting postings and comments onto Google Search results so that you can find past conversations about a specific topic.
Discord is the kind of social media site where I almost never find anyone link specific content or get hits on a search engine.
I'm curious about people starting up: Are you storing images on your own site with this instance?