Sure, but if it's the default in whatever app/browser you're using, you might not bother switching to Google as long as it gets decent results.

I suspect that this isn't the only way they determine search results :-)

My guess is that they have a relevency metric from their own algorithm, but some results return poor relevency results -- then they may go to this set of secondary results and say, "Are there any results for this query that a higher percentage than expected users clicked on" and then add those results to the list.

IOW, this data probably isn't the common case.