It’s not just Leaf Eaters either, if you look closely. Other than the Dil and Ichy pairing (which appears to be out of necessity) and the Red Claw, Screech, and Thud pairing (which may also be out of necessity), other than perhaps chance encounters (like movie VI), we have never seen a bunch of Sharpteeth work together with other types of Sharpteeth or live with other types of Sharpteeth. (Indeed, one wonders if Chomper in, the Lonely Dinosaur, was the first one to actually try it. If so, as you can see, it didn’t work well. Even that kid rejected him and had his parents chase Chomper off.)