they see them selves as the only hope of the wastelands and as tech its salvation and if they have any hope of forming a government they need their own currency
But why would they need currency?
They want something then they just take it.
And why would they need their own currency?
In Fallout 1 they traded weapons with people, what good would monopoly money do to the traders who trade with BOS?
The Caps which was the current currency originated from the Water Merchants.
In Fallout 2 NCR had expanded and created a new currency, gold.
In Vegas we have Caesars Legion who never were in contact with the NCR or Water Merchants up until now so they created their own form of currency.
But why would the BOS need to have their own monopoly money that isn't worth anything outside the BOS bunker?
There isn't any reason for them to create their own currency.
So yeah if they wanted to they could create their own but it isn't worth anything.
Their currency would be monopoly money to any outsider.