No rubbing?

Something occurred to me while I was dribbling on my front paws: how do humans know that something is theirs? How do they know that they own something?

I rub my face and body on chairs, table legs, doors, door frames, plant pots, cupboards - covering them in my lovely catty scent.
When I sniff them, I know they're mine. They smell of me.

I've never seen my human, or any other human, do this.
I've  never seen my human rub his face over his bed, his computer, the table he sits at.
How does he know what's his? What if another human walked in and rubbed their face on his things - he wouldn't own those things anymore.

I've tried to show him how to scent mark, but he doesn't seem to pay attention. Silly human.