Though it's uncertain why, exactly, that might be, the reigning theory online is that it has to do with Google's filters. According to Redditor professorzweistein,"google [sic] introduced filters a while ago that remove a lot of porn from search results even if you have safe search turned off. read more
There are no new programs, I think this is atrocious that Google knows it has an issue and doesn't even have the decency to tell us they are working on .... Block adult content at your school .... Cannot turn off safe search for several year, basically swapped to Bing to get unfiltered results for image searches. read more
Use your browser's back button to return to the Google search results page and, under the link to the page you just visited, you'll find a new option next to the always-present 'Cached' and 'Similar' links: 'Block all X results," where X is the domain name of the site. read more
The difference in search results is apparent when comparing Google's new image search algorithm to other browsers, and also to some of Google's international sites (like Google's German image search site, for example), which have not been updated with the new search rules. read more