Well private ownership of gold was illegal in 1970 for starters. Transactions in gold were never very accurate or efficient. Gold can be an ASSET and assets can increase in value. As an asset gold has lagged behind many other assets in appreciation.
Had you bought an ounce of gold in 1981 for almost $900. Today you could buy only $500 worth of stuff with it and that is after the doubling over the last five years.
For twenty five years it has been a horrible investment.
And it can decrease in value. Gold is no more immune to the laws of supply and demand than anything else. But given the fact that gold has relatively few actual uses, it has little intrinsic worth.