Bonds are valuable because the company or government that issues them signs a contract to pay out a certain amount on them. They won’t always do that, but thats why we have rating agencies to help investors understand the risk.

The closest equivalent to crypto in traditional assets is probably precious metals and gemstones, though even those typically have some industrial uses to drive demand.

Diamonds are a great example of the downside of looking at the market value of something alone. The natural diamond market has been massively disrupted by the rise of artificial diamonds and diamond alternatives.