It's certainly not just status and influence.
Sometimes you watch a group descend into being a cesspool of awfulness. The light stuff is death by boring memes, insults galore, "just an opinion" that are high-emotion crazy rants.
But the heavy stuff is worse. Watching individuals be egregiously insulted and threatened. Watching people delete their informative and well-meaning posts and never come back, because the first comment was some evil asshole having another content-free belittling attack because that's just what they do, no reason. Watching people be told they are incompetent, useless, should die, are the wrong gender, that sort of thing.
It is perhaps worse on locality-specific forums. Because then you are in view of people you know in your area, or are likely to interact with in future. Assholes don't care, and seem to enjoy the "status" that comes from putting down other people in the local area.
It does not help that such interactions seem to act like magnets in local forums, where putting people down through petty and unjustified insults attracts more of the same, and substantive interactions are lost. I guess that's because easy putdowns are low effort entertainment for some people.
But people finding themselves on the "unwinnable debate" receiving end of that sort of thing, end up leaving forums to get away from it, or are highly stressed whenever they have something to say, and may spend hours trying to carefully word everything just to avoid petty flamage from assholes and get substantive replies instead.
So some people are motivated to try to keep community areas a little gentler and cleaner. To protect and welcome others who appear to be joining in good faith, from the occasional blast of shitty replies. Like another commenter said, it's like clearing up litter when you go for a walk. Would be nice if it wasn't necessary, but because some people litter, others want to clear it up.
That's enough of a motivation for some. I've seen people spend hours moderating out of nothing more than a sense of civic duty and a desire to protect other people and encourage them to stay and feel welcomed and defended, to grow the community in a more friendly directionm, and to try to make the forum a less stressful place for new participants who have doing nothing wrong.
Like any volunteer working for something they feel is a good cause.