The probable reason why Google isn't moderating photos on Google Photos is because almost all android phones, by default, uploads their photos to the Google Cloud. Some people like to have explicit content on their android phones, and Google knows this. Suddenly having your stash deleted, or even just teenagers taking n*des, then it being saved in their photos, automatically. Google knows this better than anyone, which is why they don't moderate the content on there. There's probably a lot more than the things covered in this video, for the worse.