Just a story from Germany in early 2000. I had a website and just installed a php script to have a forum on my website and just forgot about it. Today, I could do the same, but I had a 24/7 job to monitor everything someone writes there because it could bring me personally into jail. The same with the comment section of my blog. Thats the reason why this big platforms exist and are used. Because no one other than they want to take the risk. At least in Germany are not much people that want to do that.