This argument makes precisely zero sense. We've already established that people are using site:reddit.com in search queries so the incentive already exists. And

This argument makes precisely zero sense. We've already established that people are using site:reddit.com in search queries so the incentive already exists. And frankly Reddit is already at least 50% astro turfed. But search results on Reddit are still more useful for many queries. It's also worth noting that unlike Google, Reddit has total control over the content that they're indexing. If they detect bad SEO actors they have far more power to influence them or shut them down completely because they're indexing a platform they control. Google is indexing the open web.