While I support YAGNI, I only support it when there is a copy somewhere in the source control history. I don't understand why they would permanently delete it even if they weren't planning on ever using it again? Was space that limited? Or was this a middle management kind of thing?
To be honest this is pretty normal for any modern medium. There's a period where nobody bothers to do any kind of archiving.
TV shows didn't get routinely archived until quite some time after things like "video tape" existed. Now and then early episodes of something important being discovered is news.
Most of the early history of comic strips and comic books has been lost. Original art was thrown away; modern restorers have gone through some heroic efforts to piece together archives from whatever copies of the stuff they can find.
Games? Hell, there's a not-insignificant chance nobody was even using source control until the time when video game budgets started to match feature film budgets. Companies die, and if you're lucky then someone takes home source archives. before all the drives are wiped.
