Pieces of tree can be beautiful individually, pieces of humans only when they're assembled.
Like, you can see a leaf on and think "wow, that's a beautiful leaf". You may even pick it up to admire it (especially if you're a child or a biologist). You wouldn't do that with a strand of human hair, a human nail clipping, or even less with the parts that aren't supposed to come off like hands or eyes.
Excellent shower thought, though it’s making me somewhat uncomfortable. Side note: I once read that people (men and women) see men as whole beings and women as collections of parts. I’m sick and don’t have the brainpower to look that up rn, so take it with a grain of salt
That's also somewhat to do with the concept of fetishism. Most people have never fucked someone without feet but it's not a fetish until you start all but ignoring the rest of the person in favor...
And if someone does fuck a person without feet, it's gonna be assumed that's the primary reason as opposed to any of the parts the footless (or... footloose? Sorry) person does have.