The vast majority (if not all) of subreddits I've discovered over the years has been because of getting linked to them by other users.

True moments of wonder are often discovered when linked to a subreddit that is a completely different world. /r/ooer, for example. (I'll add a nsfw warning for that page just to be cautious - I literally have no idea what's going on there).

I would never discover subreddits like that one without the help of other users.