There's no way they can justify devoting resources (i.e., staff, machines, tapes, storage space) and maintaining processes to do this when they're delivering se

There's no way they can justify devoting resources (i.e., staff, machines, tapes, storage space) and maintaining processes to do this when they're delivering services for billions of users, especially given that, as someone else has said, for privacy reasons people would assume/expect that expired data is automatically deleted.