Well, if you were living alone, in a post-apoc world where everything was in ruins, and it was common for people to scavenge supplies for survival from the wreckage of where people once lived?
I think the big problem is that the game is inconsistent.
Raiders, bandits, most people labeled as "badguys"? Sure, nothing in their buildings are marked as "owned".
Some no-name generic Scavenger, hanging out alone in a small shelter in the middle of nowhere? His stuff is Owned.
Quest-related groups who might end up as enemies or not depending on choices? Owned (The Family, Roy Phillips' crew...)
Now, people living in a town, under some sort of organization & rule of law? Sure, their stuff is Owned, and someone who knows them would either know what to do with their junk and/or it would be collected by the community.
But then you have Brian Wilkes, the little kid in the giant ant quest. He's alive - his house is right over there, with Dad recently dead on the floor. He's the last survivor of an entire community. We even learn another relative of his living in Rivit City. But everything in that town is open loot, even Brian's toys on his bed.... none of it is Owned.
So, yeah. Hmm.