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.
Good point. Tho they’re usually implied to be part of a whole that we can’t see, as if seen through a window. They take poses that only make sense if attached to muscles in the arm…