Well for one because bitcoin has no centralized observer (measurement) and each block is openly verifiable by the entire network. Each block is defined by a standard unit of measure (hashes) and has network consensus regarding said measurement. This resolves the observer problem in quantum theory.

This is not possible with gold and verification is costly and requires trust. We also cannot audit the energy required to make gold atoms as it occurred in the creation of earth. You could theoretically only capture the measurement as you transmute the gold into different bars/coinage (UTXOs).

Bitcoin is open and auditable from Genesis. Nothing is needed to calculate joules except what is already native to the ledger.