I see videos that I think are overtly sexual in nature on YouTube, even if the video is something supposedly "innocent". If you click through to their profiles there is an inevitable link to 18+ content most of the time. I am subscribed to only tech/film/gaming channels on youtube and this content is now always put into my feed. I probably have cursed myself by checking these people's profiles after the fact.
You are right though that by bandwidth, streaming services including Netflix make up the majority of data over the Internet and it is not pornographic/dangerous for children at all.
I think you really did. I don't watch much YouTube and don't use social media beside Instagram—which I mostly use for messaging friends and not exchanging photos—but I don't see a lot of erotic content on the mainstream platforms.