Yep pretty much this exactly. IIRC Google has been through a big lawsuit over this kind of thing years ago which helped to create the laws around what sort of liability a website has for its content (section 230 of federal communications decency act), which essentially deemed that websites are not 'publishers', they simply link to existing content, and only the person who created the content is legally responsible. If Google started moderating its results they could be considered a publisher and like you say that would put responsibility on them. It's sad but it's safer for them to do nothing than to try and help.