So why don't they cut out the spammy stuff like keyword links? Or, if the content is really garbage, say "no thanks"? The only reason I can see is if they're terribly desperate for content, in which case they're knowingly degrading their own platform.
There are therapists, landscapers, used car dealers, craftsmen, accountants, etc. All kinds of people are small business owners and have company blogs. Maybe they fumble around their website, but they can tell when the written content of an article on their topic (landscaping, accounting, etc.) is junk.
A tech savvy user is more likely to be familiar with the reasons and risks and ignore poorer quality writing in their evaluation.