As I said, at first glance, it seems that all cartoon films are musicals. When you think about the Disneys, they were all musicals. Then there's South Park, The Nightmare Before Christmas, An American Tale, Charlotte's Web, Anastasia, All Dogs Go To Heave, and of course, Disney's still doing it too: Frozen, Tangled, The Princess and the Frog, etc. People talk about the songs in these films. Awards shows tend to focus on the songs. Many of these cartoons now end up as live musicals too.
I'm thinking this is a question of history. I'm thinking that animated films basically were Disney's domain for so long that we began to see the Disney traits as definitional. At the same time, television was packed with shorts that were more verbal, things like Looney Tunes and The Flintstones. So these two genres developed separately and created separate expectations that we still believe today, even if they are no longer true.
Interesting? Not interesting? Thoughts?