In life you have to be rich of something, or nobody want to marry to you, and have build a family with you, you would be foreveralone, and the media would constantly mogging you over and over again for being foreveralone to remain you. And your mum would constantly tell you if you don't get married nobody would take care of you when your aged. Nobody would make a tomb for you, and when you died you would go to afterlife with empty stomach and would suffer straving too in the afterlife. That must be a lot of hurt! ouch!
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Both are the same, crypto or fiat can go bankrupt if they are not managed properly. You can be very rich by marrying a crypto-rich, but you can suddenly become poor because the price of crypto has fallen sharply. Likewise, fiat-rich cannot go bankrupt due to mismanagement.
Fiat, such as the dollar, has not been backed by gold for a long time, which essentially makes the dollar a paper. Even if it is protected and recognized all over the world. And if suddenly the whole world refuses them, as in principle, and from any other currency, then the last holders of fiat will be left with a pile of paper.
Unfortunately, digital assets such as cryptocurrencies will also not make sense if everyone abandons them.
Probably only gold will have value, even if everyone refuses it. Although in fact it has no practical value other than beauty.