We charge our customers for backup storage by volume and that includes an annual demonstration of recovery. We fire up some or all of their systems on our gear in isolation and show that they are reasonably functional.
Your teacher's comment is riffing on the well trod lines of: "heights don't kill people, it's depths that kill people", which is all about perspective. This is is not related to "guns don't kill people ..." which is about agency.
When data is lost, or decay takes over, the value can skyrocket. Depending on what is lost, someone may be willing to pay 100x when they would have spent on backup in order to get their data back, this is why data recovery services can basically charge whatever they want.
My assumption is the Venn diagram between people who pass the marshmallow test, and those who proactively backup their systems, has a lot of overlap.
On the flip side of that though, really and truly, I've restored a laptop from a timemachine backup and it came back damn nearly identical and that was magical.
I needed to temporarily move off 20TB from my NAS and bought a Hetzner storage box.
I wanted to encrypt the data before sending it so i went with the borg ssh mount. Long story short, borg failed a couple of times due to https://github.com/borgbackup/borg/issues/7672, i resumed it per documentation and got 2gb of silently corrupted data. There was no way to do data integrity checks due to broken pipes and there was no option to resume the job from the previous point either. I couldn't afford to go with the s3, backblaze wasn't an option due to placing trust into their proprietary client doing the encryption and i got majorly screwed in the end.
Also you must have been unaware of Backblaze B2? It doesn't have a proprietary client, and it launched 11 years ago only a couple months after attic was forked to create borg.