Here's a potboiler for you: Because we as humans need to bond with other humans, and in our hyper-partisan age, with politics, religion and sexuality becoming increasingly volatile issues, it's the remaining bastion of inclusiveness. We all read comic books. We all watched cartoons. I'd include things like Game of Thrones in this conversation as well (though it's not a movie). It's the kind of thing you can talk about at the water cooler without being deemed a racist or bigot (by your Democrat/liberal friends) or a commie or bleeding heart (by your Republican/conservative friends).
It's a detachment from an increasingly isolationist society (I also would say something similar about a lot of the nonsense - challenges, memes - you see on social media).