Demand and supply play roles in setting market price of an asset. When a supplier says “fuck it I would rather shutting down my business than lowering my sell price because it doesn’t make sense” is where the “backed by” comes into play in an intuitive way. The selling price has to make rational for running the business.

Gold production varies but cost of mining difficulty stays the same as global miners grow or shrink.

While for bitcoin the production reduces by halving no matter what and mining difficulty varies as global miners grow or shrink.

Not many things can crash gold mining expenses. Only thing can crash bitcoin mining expenses is difficulty declining faster than halving.