As the title suggests, any society and it's economy are one in the same. Two words, same concept. To truly understand this, you must first be willing to see what drives people together; what makes us want to be around others.
Alone we can survive, more or less. Depending on where, and one's ability, that "Survive" can range from "just barely" to "thrive", yet even in that "thrive" category,we still want more stuff. Better shelter, better food, better tools, more leisurely time, ect...It's this greed which drives us to work with others, to share in the responsibility of surviving so that we might both be able to "get more stuff".
Take away this need, and you take away society. In a truly post-scarcity environment, people wind up being hermits with little to no social interaction. Of course, that's a moot point as there will never be a post-scarcity environment.
Which is not to say anything negative about start trek, mind you. In fact, it's flawed concept of a economy-free society is what first got me thinking about this stuff, and underpinned my explorations of economics and society for decades to come.