There are millions of users on YouTube, if not billions. Not all of them are over 18. It is so easy to lie about your age, or to allow someone under 18 to use your account if you're over 18. Just because you watched endless hardcore porn or extremely graphic violence when you were a kid and you turned out fine doesn't mean everyone else will. You're just one person, and there are eight billion people on this planet.
If you were a parent, you probably wouldn't be making this meme. If you are a parent, and you still think using AI to stop kids from seeing things they shouldn't see is wrong, I have five words for you, words you might have heard from the 1975 film Jaws:
"YOU GOT ANY BETTER SUGGESTIONS?!?"