Money solves three problems at once.
It remembers value across time. It connects people who want different things. It compresses incomparable goods and work into a common unit. The coin, note or database entry is the interface to those functions, not their ultimate source.
This is why a bank balance can buy a house while being only a number. It records a claim inside a network that expects the claim to remain legible and acceptable.
Trust made transferable
Without money, exchange often requires a double coincidence: I want what you have, you want what I have, and we agree now. Money lets one transaction leave behind a portable memory that can be used with somebody else later.
The compression is powerful and lossy. A price makes comparison possible while forgetting need, effort, ecological cost, affection and power. What cannot enter the unit becomes easy to treat as valueless.
Monetary crises expose the substrate. During inflation, the unit’s memory degrades. During a bank run, people doubt that recorded claims can be honoured at once. During currency collapse, notes still exist but no longer coordinate future acceptance.
Cryptocurrency changes the memory mechanism. A distributed ledger and fixed issuance rules can reduce reliance on banks or states for certain operations. Users then trust software, key custody, consensus, exchanges, governance and future demand.
The trust did not vanish. It changed form.
Money is useful because strangers can rely on a shared memory without knowing one another. The political question is who may write that memory, whose losses it forgets, and how people recover when the number no longer means tomorrow what it meant today.