Most people in entertainment don't have healthy relationships. And/or have no idea how to write them. So they're pretty bland and empty when they write them.
Also, people just kind of end up in relationships, go eat, and fuck a lot. Can't really put that in a cartoon or comic.
So they like to use toxic relationships to fill all that space.
And vewiers like it becuase they dont know how they will end.
And studios like it because they're not obligated to see the relationship to the logical conclusion of weddings and babies.