It's digital money that's accessible from your phone / usb dongle and there's no custodian (a bank) to act as a middleman to ensure it's safety.If someone steals your phone, computer, laptop, dongle, that's it.They have access to all of your wealth.Sometimes they don't even need to physically steal those things because they can just hack into those devices over the internet.At least with fiat, there's a bank holding your money and you have to prove it's you when you withdraw large sums.You can also keep cash in your and keep a smaller portion on you that way if someone steals your wallet, you've still got the bulk spread out at home and in the bank.If they steal your crypto wallet, it's game over.
You're right it's a terrible idea and you shouldn't ever buy any.
