The point of content marketing blogspam is to pester the reader with AdWords and the occasional affiliate link.
Old-school useful content is rarely monetized, just someone sharing their passion for something. Occasional affiliate link, with the obligatory apologetic "hey web servers cost money, so I included some affiliate links here!"
The uselessness is just a side effect of Google directing you toward paying customers.
You're thinking of Content Farms. I think the current villain is Content Marketing, which is to attract people to your website without paying for AdSense, via an inane blog post. Like the Michelin guide or Guinness book did before the internet.
The reason Google keeps those results near the top is because it drives up the cost of AdSense, since multiple competitors are fighting for the first page of organic results with those tactics, and AdSense is a way to "cut the line".
The result for users is that the first page of most result pages is littered with advertisement, either via real AdSense or with those inane marketing blog posts.
Old-school useful content is rarely monetized, just someone sharing their passion for something. Occasional affiliate link, with the obligatory apologetic "hey web servers cost money, so I included some affiliate links here!"
The uselessness is just a side effect of Google directing you toward paying customers.