Because of those properties they become a store of value (representing the work and rarity) which then makes them a useful proxy for trading that value, which increases their rarity/value by taking it out of circulation when used as a store of value.
The difference being the currency in this case has no inherent value to fall back upon.
For one, gold, enables the electronic device you used to post your comment.
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.
That's what interesting - only a tiny amount of gold is needed. This wouldn't work with lead.
>this doesn't explain why people were greedy for gold thousands years before.
You're asking me to do this research?