Fortunately it seems that they will always find people for that, because their subreddit revolves around something they like, and they will often do a good job

Fortunately it seems that they will always find people for that, because their subreddit revolves around something they like, and they will often do a good job (it seems) because they want to promote that hobby, not that it will directly benefit them financially (example, moderator of askhistorians). Yup. I'm one of the mods for /r/AskEngineers. I want to promote engineering in general: designing things, fixing things, learning how things work. I'm glad to do this, and to encourage good and useful discussions. I especially like when we've got questions from engineers who are working outside their own discipline, and just need a little nudge in the right direction. Getting just a paragraph from an expert can save days or weeks of effort.