I seriously don’t get shipping in the western cartoons enthusiast scene in particular, but this expands across like any other medium. It feels like almost any and all conversation revolving a given medium in famous serious gets monopolized by people who want to see x character date/have sex with y character. Very little conversation occurs about the plot, the animation/screentography, special effects, or themes in a given medium for modern series.
I understand human relationship is a very big deal about the human experience, but it’s almost always going to revolve around intimate relationships with some sexual connotations and none about colleagues or close friends.
What is the reason for shipping having a huge monopolization of online fan discourse? Why is it more appealing than other topics on a given medium?
If you're talking specifically about western cartoons, probably due to the target demographic having no prior experience with romantic relationships, and/or just experiencing romantic feelings for the first time.
As for older fans, using their favorite characters as surrogate family.