Google results are not polluted with spam because Google doesn't know how to deal with it.
Google results are polluted with spam because it is more profitable for Google. This is a conscious decision they made five years ago.
because it is more profitable for Google
Then why are DuckDuckGo results also (arguably even more so) polluted with spam/scam sites? I doubt DDG is making any profit from those sites since Google essentially owns the display ad business.
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