Possibly a similar process to when you go into an AWS account, and find dozens of orphaned VMs, a few thousand orphaned disk volumes, etc., saving like $10k/month just deleting unused resources.
We've all been there Jeff.
In this case, I don't think it was forgetfulness; unlike us, they have an excuse and they were trying to optimise for disk seek times.
Anyway, I've got a half-dozen cloud accounts I need to go check for unused resources waves.
It's not a case of forgotten data, it's duplicated for access time reasons, like with optical media.
It follows in the footsteps of trading in storage for less compute and/or better performance.
An opposite approach in the form of a mod for Monster Hunter: Wilds recently made it possible [0] for end-users to decompress all the game textures ahead of time. This was beneficial there, because GPU decompression was causing stalls, and the trading in of compute for less storage resulted in significantly worse performance.
[0] https://youtu.be/AOxLV2US4Ac