Is monetising the web through advertising the reason these scraper sites exist? And removing that would make scraping sites an expense with costs rather than profits?

Perhaps google could do this. Ads on third party sites are probably a small part of their income compared to sponsored ads in search results, so they could be sacrificed and they’d take down their competitors who rely more on the website ads because they don’t have the search?

However, they have no need to compete on search quality at this time. If another player in the search and browser wars started downweighimg ad heavy sites then this might make google have to reluctantly follow suit. But you can imagine the FUD campaigns to paint such an actor as killing the internet and being the bad guy etc…