Too bad Google doesn't make more people aware of these features.
If you search without much thought and click on whatever is at the top of the page Google's biz model works.
If Google teaches people to question the veracity of the results, use advanced Boolean searches & other filters, etc. … it wouldn't take much for their biz model to stop working.
The more same the results are the less risk Google is taking with any search. So long as any sort of diversification is largely tied to prior user behavior or location they show enough diversity to where they can keep homogenizing the rest of the result set.