Because all the dinosaurs has their mouth open and with that jaw, t-rex looks boxlike that way maybe? dunno.
Like, seriously, why
is that snout
It’s something I always noticed growing up, too, and I have a few theories:
One is that Fantasia, at least, was animated over half-a-century ago when we didn’t know nearly as much about how dinosaur anatomy in-general worked. I mean, the fact that the t-rex isn’t animated with his tail always dragging on the ground is an absolute miracle, he kind of whips his tail around like he’s some sort of mammal which doesn’t make sense, and there are a lot of “mistakes” in The Rite of Spring that would make anyone with any dino-sense now laugh hysterically but were accepted as “fact” back in the ‘40’s when this was being animated.
My other theory kind of ties into the previous one: in the ‘80’s and ‘90’s when Land Before Time and We’re Back were animated, the jury was still out on whether dinosaurs were more related to reptiles or birds. The general public still assumed that dinosaurs were big, dumb, cold-blooded, scaly reptiles and that means that most people in studios making movies to appeal to the general public would assume this in their designs. If you try and break down a lot of reptiles into very basic shapes, you’ll find that their heads are usually a nice box or rectangle-shape (actually if you get technical it’s usually some sort of diamond-shape, but that’s getting nit-picky.) We don’t have dinosaurs to base our animation-designs on, so at the time we thought the closest proximity would be reptiles.
And I think that being an animator you can sympathize with the last theory I have: it’s easy to draw features on a box-shape and keep it in-perspective and recognizable from all angles. Up until about two decades ago, using any sort of computer to help you animate was totally out of the question (and even then it wasn’t until about ten years ago that it became so prolific), so every little tiny detail was animated by hand, and that meant sometimes you had to make things easy on your animators. If you as a studio are going to have to break the budget just to make sure the dino’s “look right” and not have money to actually do anything else, you’re going to find ways to make it easier on your animators - and that includes box-face t-rex.
Also I think I remember in We’re Back that the t-rex’s features became much softer and “cartooney” when he was given the power of speech, so I bet there’s some psychology behind the box-faces: maybe such angular designs usually make audiences feel more uncomfortable about the character in question - but that’s just purely speculation.
I think ignorance does a lot to art, especially animation or movie-design - it ages it, it encloses it in a “time-capsule” so that when we look back at it we’re peeking back into time. I mean, just think how awesome and “accurate” the “velociraptors” in Jurassic Park looked two decades ago: and think how any paleontological artist worth their salt steers clear of that design now - and Steven Spielberg even consulted with Jack Horner!!! (Fun movie fact: toward the end of JP, when the “velociraptors” are hunting the kids in the kitchen, there’s one that looks around a corner and nearly catches the kids - it even seems to sniff the air, right? I guess originally Spielberg had directed it so the dino’s tongue flickered out like a snake. Horner told him that was a huge no-no, and reminded him “they’re closer to birds, not snakes.”)
It’s interesting though, because I bet in another fifty years there could be another animation student looking back on the films from our time wondering “why in the world they animated dinosaurs like this”. Like…. What sort of things about dinosaurs do we accept as “fact” now that will be debunked in the next few centuries?