Google generates revenue via ads (or analytics, which helps Google target ads down the line), which lame results often include. Downranking ad-supported websit

Google generates revenue via ads (or analytics, which helps Google target ads down the line), which lame results often include. Downranking ad-supported websites in favour of ad-free one would cull a lot of spam and would be trivial to do, but yet Google isn't doing it. Curious right?