SEO'd garbage often contains ads, including
Google ads. There's no incentive for Google to fix this problem.
Google's job is not to give you great search results, it's to keep you clicking on ads. Ideally it would be the ads on the search results page directly, but if that doesn't work then a blogspam website with Google ads is the next best thing.
If Google was a paid service this problem would be solved the next day. Oh, and Pinterest would completely disappear from Google too. :)