As in real banking system.
The banker pays a rate of interest on deposits
The banker receives a rate of interest on loans
People receive a rate of interest on their deposits
People pay a rate of interest on their loans
Here the bank is just to vaporize money out of the game to hide billions. And with all those billions the capital is so abundant that the demand of money is very low. So nobody asks for loans.
And this lack of physicality is another problem. There is a teleport for bank accounts that are ridiculous in a game based on pirates if all the game was based on living in a port and having to expand this port with a fort, having banks that hold gold that will be invested on the fort or on other buildings or plantations or in buying new ships. Of course the port will need protection but also funds to pay military Navy. Then so a trade system to make profits,... and so the money would be in banks yes ! But it could be plundered cause it would be phisically on the map, like buried treasures.