Population dropped a lot after WW III, and society shifted with the expansion and technology improvements.

Worlds in the Federation are mostly post-scarcity, because when you can use abundant energy, produce just about anything yourself, and I suppose automation as well, your focus changes to self worth, discovery, and improvement vs. survival.

But worlds outside the Federation aren't quite that level, for whatever reasons. Politics mostly, probably. Some aren't that great.

Yeah you kind of have to assume that, in the depicted post-scarcity society, any “job” you see people doing is something they want to do. Like, Picard owns the vineyard or whatever but all those people in the fields might be people who like making wine and so Jean-Luc opens the land for them to do this.

Sisko’s dad has a restaurant in a society with replicators. Clearly this exists because he likes making food for groups of people.