People consistently underestimate the many ways in which storage can and will fail in the wild.
The most vexing storage failure is phantom writes. A disk read returns a "valid" page, just not the last written/fsync-ed version of that page. Reliably detecting this case is very expensive, particularly on large storage volumes, so it is rarely done for storage where performance is paramount.
Not that uncommon failure mode for some SSDs, unclean shutdown is like a dice roll for some of them: maybe you get what you wrote five seconds ago, maybe you get a snapshot of a couple hours ago.
Early SSDs were particularly prone to phantom writes due to firmware bugs. Still have scars from the many creative ways in which early SSDs would routinely fail.
In college I had a 90GB OCZ Vertex, or maybe it was a Vertex 2.
It would suddenly become blank. You have an OS and some data today, and tomorrow you wake up and everything claims it is empty. It would still work, though. You could still install a new OS and keep going, and it would work until next time.
What a friendly surprise on exam week.
Sold it to a friend for really cheap with a warning about what had been happening. It surprise wiped itself for him too.
The most vexing storage failure is phantom writes. A disk read returns a "valid" page, just not the last written/fsync-ed version of that page. Reliably detecting this case is very expensive, particularly on large storage volumes, so it is rarely done for storage where performance is paramount.