But why would that Picasso have any value? You can't show it to others and it's difficult to resell it. And if the cops find out that you have it - they will confiscate it.
In many cases there's also a reward for any information regarding the stolen artwork. So that makes it even harder to resell those artworks.
The world is a big place and the rule of law we trust to just work in the West is certainly not the norm everywhere.