A door-and-lock is a single-agent system and therefore isn't a good analogy. Money always needs social consensus. In a blockchain, you're relying on others agre

A door-and-lock is a single-agent system and therefore isn't a good analogy. Money always needs social consensus. In a blockchain, you're relying on others agreeing on a certain history. That society can decide to disagree with you and consider a different history as truth. It has happened multiple times on Ethereum and Bitcoin both.