Coz it is an expensive metal which no one has ever disagreed before, meaning everyone accepted the fact that it is EXPENSIVE.
a) Gold is RARE,
b) Gold is indestructible so it lasts forever
c) Gold is extremely Malleable that it is mostly used in Electronics, Jewelry and Furnitures among others
GOLD is very expensive to mine, extract and process.
Because Gold is indestructible by any of the "natural elements", GOLD is used to determine how much money a country can produce in ratio with the country's
GOLD RESERVE.