I once asked one of the original YouTube infra engineers “will you ever need to delete the long tail of videos no one watches” They said it didn’t matter, because the sheer volume of new data flowing in growing so fast made the old data just a drop in the bucket
The energy bill for scanning through the terabytes of metadata would be comparable to that of several months of AI training, not to mention the time it would take. Then deleting a few million random 360p videos and putting MrBeast in their place would result in insane fragmentation of the new files.
It might really just be cheaper to keep buying new HDDs.