The reason Google shows you search results is to serve you ads, but the presence and volume of ads is an inherently negative quality of those search results. So Google is incentivized to show you lower quality search results, as long as those results don't become so bad that you stop using the service.
Endless terribly formatted clones of Stack Overflow or GitHub issues don't provide any value to the world, but they do show Google's ads, so they weren't banned from all results after the first person at Google noticed them.
Empty results pages don't lead you to ads, but ad spam that doesn't answer your query does, so over the years the "no results" page has more and more been replaced with useless results. Some of us spend some mental energy looking at the SRP to determine they're useless, many more probably click the first result and are served ads.
Google's founders knew this, wrote it into their paper, then ignored it and made it their business model anyway.