Similar to gold, Bitcoin has a very finite supply with a total of 21 million BTC that ever be in circulation. At Bitcoin’s current mining rewards rate of 6.25 BTC per Block, Bitcoin’s annual production is equal to Gold.
This is one of the many reasons why people refer to Bitcoin as “Digital Gold”. In addition, the fact that BTC the first cryptocurrency. By and large though, the primary reason for this nickname is due to the scarcity of supply.