There's a lot of articles on this, the belief is that children crave predictability so they re-watch movies to the point that they can predict everything that will happen.
Adults crave predictability too; they've just seen enough stuff to be able to predict most of the things one encounters out in society.
But watch a YouTube video of a magic trick, and you'll likely click back and re-watch the critical moment a few times before you've even realized what you're doing. Even if you don't end up understanding what happens, your brain inherently wants to make sure you are entirely clear on what you saw, so it can learn the raw fact that "this is a thing that can happen" and then attempt to reconstruct your mental models and schemas to take that evidence into account.
Teacher here. Even most teenagers crave predictability (and structure) though they would never admit it or even be aware of it. I imagine it’s much easier to push and test boundaries when you know exactly when and where they are. Easier to “rebel” when you know the time to rebel is from 11:15 to 12 and then you can take a break and go get lunch.
I've read somewhere (forget where) that the key to successful pop music is the slight unpredictability of new songs. That new hit song is mostly familiar… but just unfamiliar enough that you need to re-listen to it 100 times to really wrap your head around it.
https://parenting.blogs.nytimes.com/2009/11/12/kids-and-movi...