Gold cannot be inflated by printing more of it; it cannot be devalued by government decree, and unlike paper currency it is an asset which does not depend upon anybody’s promise to pay.
Portability and anonymity of gold are both important, but the most significant fact is that gold is an asset that is no-one else´s liability.
All forms of paper assets: bonds, shares, and even bank deposits, are promises to repay money borrowed. Their value is dependent upon the investor’s belief that the promise will be fulfilled. As junk bonds and the Mexican peso have illustrated, a questionable promise soon loses value.