Title says it all. Why does Google continue to let Pinterest dominate search results on Google images? Similarly, why does Google allow Yelp and Quora dominate search results while heavily penalizing almost all other results which are behind pay/sign in walls? Further, Google seems to have decimated forum results (unless you append "forum" or "reddit" to your search), but how do forum results differ from Quora, Pinterest, and Yelp, which are crowdsourced, user generated content?
Of all the offenders in bad search quality these are hardly the worst offenders. The throwaway SEO’d affiliate blogspam and factory produced Medium articles are much worse.