This question has been asked ever since Bitcoin’s value as a Cryptocurrency increased in a short period of time.
Since time immemorial, Gold has been the standard currency even if it a commodity. In times of war paper money, share in stocks market will be useless also during Extinction Level Events. Even during these catastrophic events, bitcoin will also be useless. If the internet goes boom and ceases to exist. The transactions made by Cryptocurrencies and Digital currencies need the internet connection to the process. Also, gold has a physical form. It is tangible and it is accepted globally.