So money would be a bit pointless
Not everything is universally available in the Star Trek universe. For me, an unsolved problem with the Federation economy is real estate. Why does Picard's brother live in a manor house in a vineyard? Why not someone else? Why not me? I want to live in a vineyard.
It wouldn't matter how many planets there were in the Federation. There would always be more people than planets, there would always be planets which are more desirable than others and there would always be particular places on those planets more desirable than other places. Who gets to live where? Who gets to own land to run a vineyard, instead of there being apartment blocks or suburban housing in the same place? It's never addressed beyond a vague sense of it not being a problem.
I think the Ferengi economy is actually the curiosity in this setting ; it seems to depend on artificial scarcity (and repression of entire social groups, from the way they treat their women).
I don't think it's a curiosity, it's deliberate. Narratively, the Ferengi business and economy is a deeply engrained part of their culture. Metaphorically, the Ferengi are us in the present day. They don't do business because they have to, they do business because they want to. Money is how they keep score. It's how we keep score.
Ask five economists and you'll get five different explanations (six if one went to Harvard). -- Edgar R. Fiedler