Not sure I get why this is necessarily a problem. Isn't a bank vault “someone else's safe”?
Huge corporations (banks included - there was something that happened in 2008 as I recall?) crash and burn.
Banks and their vaults are covered by legislation.
100s of millions of people lost their money though perhaps not their valuables in storage.
Let's see what happens if google or aws loses all your photos in a server glitch (this happens).
"the cloud" is not some magical faerie land where only good things happen.
Shit happens in the cloud too.
The point is that all media are vulnerable. Someone else's computer might be a bit more safe than your own but it is not guaranteed.
Prints and negatives are subject to loss, fire, theft, physical deterioration and angry relatives.
Tapes print through, stretch, get lost, jammed, burned.
Cds/dvds deteriorate, the dyes fade, get lost scratched burnt stolen cracked.
Hard drives crash, get subject to bit loss, are vulnerable to magnetic fields, static electricity and other emc issues.
Servers and server farms and hot sites flood, burn, lose power, have their ups' fail, don't pay their electricity bills, individual psus die, explode, burn, chips fail, ram fails.
Companies go into liquidation, lay people off, have crap employees who are negligent ...
File and disk and tape formats change, become obsolete, hardware can't be found to read it ...
People die and their passwords die with them, or nobody knows they had a million photos in a cloud somewhere.
So you take the best steps you can to ameliorate risk and hope for the best.
As for me, i remember that there are billions of prints and negatives from the past 100 years still in attics, drawers, in cupboards and under beds, billions of others have been cremated or dumped in landfill.
The question does deserve to be askedt- why bother worrying?
You think your family in 100 years time are going to be looking through your digital archive of half a million pics? They'll be too busy catching rats to eat and gathering rags to wear.
Historical value? (the "doomed to repeat" trope)
There are extensive archives available online and in museums and other places that document the Nazi atrocities of WW2. People are shown them in schools.
That doesn't seem to be stopping up descending into further atrocity as I write this.
You know ... Just worry about something that matters is what I think.
It's being so cheerful that keep me going.