^ Aye, good point. My only answer would be that if they've gotten
that much over money back home on Sol III that humans have been conditioned from birth to live without money, and that the state provides for them whatever they want through replicators anyway (Want a new set of curtains? It's as easy as clicking your fingers), then maybe this hypothetical ''Ship's Petty Cash'' pool
can be used for personal purchases, because the Federation isn't really that bothered what it gets used for. It's just that Starfleet officers need access to *something* currency-based, for those occasions when they need money while out there in the great unknown.
The Vanderbeltians ( let's call them that

) with their thriving money-based economy aren't gonna take kindly to Starfleet ships rocking up on their doorstep and trying to barter Katarian Bobblebeads in exchange for their favor. Neither would the Barzans be inclined to even have the Federation at the table to buy their wormhole if they were the only guys who didn't have money in their pockets. So, there are definitely times when even the enlightened 24th century types need to bring out the Benjamins, digital or otherwise.
The ultimate irony is that the Star Trek show which
really went to town on the whole ''Humans Don't Use Money/Humans Don't Want For Anything'' philosophy, had a scene
in it's very own pilot episode where Beverly peruses an exotic alien market bazaar and says ''Charge It To My Account!'' when she sees some shiny fabric that she likes.
