In the end, you can't eat fiat money either.
But you can buy food with it in the grocery store in the corner. And you can eat that food. As I currently know none of the grocery store are accepting cryptocurrencies as a payment method. This would be one of the best use cases for cryptocurrencies. And if the stores, markets and restaurants would accept cryptocurrencies, then we would not need to sell cryptocurrencies for fiat money. We could use cryptocurrencies directly.
RE: The Market Is Exposing Some Of The Issues With Cryptocurrency