"there's no spam that doesn't try to promote something" is, unfortunately, not true. Or at least, some spam plays the long con. On sites where karma or social graph confers advantage, bots will harvest one or both through low-effort, high-payoff posts. Various disinformation and distraction campaigns may sell only confusion, discord, or volume of content. And if it's the graph itself or specific connections which matter, ossiby for hishing, recruitment, or other compromise, you'll see other behaviours.

Not all media manipulation is commercial. Not by a long shot.

You're fighting the last war, if not older.