SEO spam doesn't exist because Google sells ads. SEO spam exists because there's money in getting people to visit your site and Google is the largest search engine.
SEO spam is also something Google themselves are already generally incentivized to eliminate. It's not like their ad model does better if users lose faith in their results.
> It's not like their ad model does better if users lose faith in their results.
Yes but not really: if the results are so bad that they're useless, yes, the users leave, but Google profits maximally when the results are only barely good enough that you don't leave but still filled with a ton of ad-bloated crap.
SEO spam doesn't exist because Google sells ads. SEO spam exists because there's money in getting people to visit your site and Google is the largest search engine.
SEO spam is also something Google themselves are already generally incentivized to eliminate. It's not like their ad model does better if users lose faith in their results.