Cash is eroded away by inflation. If your currency hits high inflation for years continuously, like we had in Iceland (yes, I'm from there), going up to 25%, your cash isn't worth shit in 5 years time.

I've experienced that. My parents experienced that. They had no "investments", kept their money in low-interest savings accounts, yet somehow their life savings was no longer enough to buy a used Toyota.

Want to get more strange? What about war? How much is your money worth in case WW3 breaks out? Hardly likely? sure. Is it possible? absolutely.

The point is, nothing is "safe", just different levels of risky.