Honestly I'm not sure they could: unlike The Feed which is something you look at when you're bored, search results don't benefit much from the normal click maximizers - i.e. "What you read next will SHOCK you!" isn't a useful result when I'm searching "difference between lawnmower blades".

We're basically there already as far SEO spam goes, and Google goes to some efforts to try and minimize that because it's a bad search experience and drives people away.