Symbolism, Imagery, Allegory
You've got ears, right? How about a nose and maybe some eyes? Well, if you're a rabbit or a bear, not much else matters. The best and most respectable animals, according to these two, are not those that have great moral character or intelligence or anything like that. They're the ones with the best features.
Think of it this way. For years, you work and work, saving up so that you can buy a super fancy car. Finally, the day comes. You skip on over to that fancy Tesla dealership and you drive off the lot with a car that's elegant, streamlined, fast, eco-friendly, and generally just everything modern engineering can be.
But when you swing past your friend house just because you happen to be in the neighborhood, you don't brag about any of these features. Instead, you say, "Guys, you've really got to check out the cupholder inside this thing. This is the best cupholder on the market. You pull this thing back and it's gone!"
What we're saying is rabbits, bears, worms, and Teslas are more than just a single feature the dealer threw in at the last minute to get you to pay a little bit more. We're a bigger whole. So when Seuss focuses in on ears, noses, and eyes, what we're really looking at is a symbol for a dinky part that's never going to satisfy the greater whole on its own.
Because, you know, a nose is a nose is a nose.