Because google already has enough control to destroy the business of these websites. Not getting into the carousel is a pretty serious dent in the business of many websites (because their competition will, and any website below the carousel is going to get a fraction of the clicks of one in it).
If google required a blood sacrifice to get on the first page of results, a huge number of websites would reply "animal or human?"
If google required a blood sacrifice to get on the first page of results, a huge number of websites would reply "animal or human?"