Digital Gold team only does market making and as they said they are still working on integrating their market-making algorithms through APIs on Catex. But they shouldn't be held responsible for the volume on exchanges. They will only do market-making which means ensure the liquidity (have buy orders in place close to the real market price of GOLD).

Moreover Cryptex and Livecoin exchange are more popular exchanges than Catex and Coinsbit so obviously you should expect them to have more volume