Because the funds up to 100k euros (in my country) are guaranteed by the central bank.
This is the amount I know it's safe no matter what.
What you do beyond this point ... your risks.

And if banks would be giving you a 60% interest that would bring also the inflation close to the same level.
Meaning that while you will be earning a lot from your deposits everything around you will become far more expensive.
In the end it will be a 0 sum game.