Interesting observation. Just imagine if google search was more engagement driven. It’s pretty great that it is only so to a small degree (in the sense of figuring out what links people are most likely to have been searching for, which is sort of a case of that positive feedback loop in engagement systems)

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.