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This is partially by design. Every time Google says "hey, do this and you'll get an SEO bonus", everyone and their mother scrambles to do that so much they beat it into the ground. Remember Google Authorship? Freaking content mills were getting their unpaid freelancers to sign up just for their SEO benefit.

Google just, in general, wants content to be of value to their users. If a web searcher performs a search and clicks on a piece of content, and that content isn't any good, that user is going to lose some trust in Google. Individually, that's nothing. In aggregate, it could greatly diminish Google's market share, so they want to avoid it at all costs.