Converting your bitcoin to gold with Coinapult and holding a gold balance at Coinapult allows the user to retain his or her purchasing power in terms of gold (i.e., not be subjected to the volatility of the bitcoin market). Being able to convert any amount of this gold balance back to bitcoin instantaneously at any time allows the user to spend that value using the Bitcoin network. 

While physical gold feels nice in one's hand, it cannot be spent using the Bitcoin network! :)