Human claws

I was looking at my human's claws today, on his upper paws, and I noticed that they were shorter than when I saw them yesterday.
I blinked at my human to show him that I'd seen this.

I has a confused though.
I never see him clip them, and I've never seen another human clip them for him. How did they get shorter?

I never see him scratch anything with them, either - not a chair, a bed, or a tree. How does he know what he does and doesn't own?

And his claws don't retract. They just stay there at the end of his paws.
What's the point of human claws?
Humans are odd.