For that side of reddit, you’re right.

But for the uniquely useful side of reddit, federation won’t help. If I post a question like “how do I get this obscure game to run well on this obscure Linux distro?”, nobody is going to repost that for me, and if I don’t maximize the amount of eyeballs on it, it’s unlikely I’ll get an answer. My best choice is to post it on reddit, either in /r/linux_gaming or in the specific game’s subreddit.

I assume that most users who post anything at all on reddit do it to ask questions like that.