This would basically be me explaining it to you... (I know it's NFTs, but same difference)
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But for real, I do know one thing: Crypto isn't backed by any physical item. So there's nothing to trade it in for - you just have to hope that you can sell it before the currency calls it quits one day.
Bitcoin DID make a physical "coin" you could buy which had a code on it. But it was basically like a gift card, so once you redeemed the code, giving the coin to someone didn't transfer the value with it.
All in all, I'd say it's just a way to quickly move cash without attracting the attention of the authorities. But not something I would keep in the long run.