* Some of that skew might be their algorithm noticing that the great unwashed masses are looking for ecommerce*
Not necessarily. The great unwashed masses may not be searching for ecommerce, but people not searching for ecommerce may not be monetizable.
Let's say we run a basketball web site that has a search engine. People sometimes type the word "travel" into the search bar.
We can show them results related to the rules violation of "travelling," and/or results related to physical travel such as "trusted partners" who provide charter trips to playoff games.
It could be that we know that 90% of the searches for the word "travel" are for the rules violation. But the remaining 10% are the ones that click on ads. And we get a kickback when someone clicks on an ad on our site.
If all we care about is the web site's revenue, we might choose to prioritize showing travel to basketball games, even though we know it's only relevant for 10% of the users who query the word "travel."
It may only be 10% of our users, but it's 100% of our revenue from keyword searches for "travel." So we show the monetizable results, and maybe--if we are feeling generous--we'll show a little line, "Showing results for travel to games. Click here to search for travel (violation)."
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TL;DR: We don't need to assume that Google is trying to provide good search results for everyone. They might be trying to provide the results that maximize their immediate revenue.