After looking at Google’s search results quality i can understand why webmasters, desperately, spam backlinks to rank their websites.
Usually, Google’s top 20 results are on topic but from there it all goes downhill.
From top 1000 results usually around 950 are absolute garbage, nothing related to the original search. Just some loose keyword matching.
Google is showing a lot of bad results, dead sites, not updated sites, etc.
And the working webmaster is desperate to rank his well updated, on topic website.
What to do ? Buy Adwords credits or spam links hoping to rank better? The answer is pretty obvious.
Moral of the story : If google wants less spam than provide some better quality in their results.