Digital Money or Cryptocurrency has value for being as valuable as money. Cryptocurrency has the properties of money that is durable, concise, exchangeable, rare, divisible, and recognizable based on mathematical formulas rather than based on physical form (such as gold and silver) or trust in the center (such as fiat currency).
Digital Money or Cryptocurrency is supported by math. With these attributes, all that is required of money to have an exchange rate is trust and acceptance.