Productive assets have earnings. Earnings can compound. A common stock share (or mutual fund that holds them on your behalf) hopefully has earnings. Like farm land has earnings. These earnings can be reinvested causing growth.

Gold is not a productive asset. It is cash like a 20 dollar bill is cash. Cash is a non productive asset (unless it is loaned out with interest paid). Gold produces nothing. It just is. An ounce of gold 200 years ago is still an ounce of gold today. And I am not talking about numismatic value of some coins that collectors pay a premium for their rarity. Just an ounce of the commodity gold.

Gold would not be a good thing to hold if a person is trying to grow a business and has a profitable business to grow. Gold does not "grow" wealth. If a person is already wealthy and does not want to lose their wealth (to hyperinflation, stock market crashes, government inflating the purchasing power away from paper currencies, etc. etc.) gold can be a strategic portion of a balanced portfolio. It is one reason central banks hold gold as a reserve asset. It is a foundational cash asset, recently advanced to a tier one bank asset again. 

Maybe the central banks don't know what they are doing????*****

Edit:  Disclaimer: That is my understanding which could be wrong. I am wrong a good portion of the time. So best just disreguard my posts as many are probably wrong.