They never look at what a moneyless society would actually be like. It is never explored in any dramatic or intellectual way. They simply use it as a sort of "buzz word" to imply how enlightened and noble the Trek characters (and, by extension, we Trek viewers who "get it") are compared to typical, unenlightened modern humans. It smacks of cheap flattery. It makes me think TPTB thought their base audience was only nerds who think they are different and more enlightened than the rabble around them.
It is not an attitude I notice in every episode, but it does appear quite often. And it is
an invention of the later Trek shows; I never got the impression that TOS ever aimed at such a limited audience.