I've been keeping all my physical art archived for a decade now because I don't ever want to lose them! To me its good to keep the old stuff so I can both have a point of reference, as well as old concepts I might not remember on hand anymore, or I want to show people some of my old works. During a time where I was digital only, I ended up deleting my account that had all that art on it, and then my computer died after. I lost a whole years worth of art, and I will always regret not backing it up. I have also lost some physical art due to moving or things getting misplaced.
But not anymore!!! I got a huge filing cabinet so I don't have to lose any of my stuff!