They're relatively useless for other purposes. Eg, gold is rare, heavy and malleable. In situations where you need those qualities other options exist, like lead. It has the advantage of not oxidizing, so it makes for great jewelry.

But all of that is extremely contextual. If it turns out there's a huge reserve of it somewhere, it will crash in value. Or if things crash badly enough there may be other things to worry about. Eg, a community that desperately needs water is probably more interested in pipes than gold.