> Arguably, the purpose of a search engine is to help 
    > people find sources that they don't already know about.

I certainly don't want that... I want a search engine to show me a set of results likely to be most relevant to my query and to my interests. Google does some limited randomization of results to prevent winner-begets-winner outcomes (based on my SERP result research) but they're purpose is certainly not to show people sources that they don't already know about. Most of these queries are basically "navigational" anyways: is someone searching for "trump tariff" looking for interesting results or are they looking to navigate to a story about "trump tariffs"?