> Currency was later re-introduced to enable the Ferengi race to be portrayed as greedy merchants.
I don't think that's really accurate; the Ferengi were portrated as greedy merchants focused on profit starting fairly early in TNG without direct reference to currency (gold -- not the later "gold-pressed latinum" -- was mentioned, IIRC, as an item of interest, but not in any context which implied it was used as currency); I think gold-pressed latinum as introduced as a currency in DS9 because DS9's role as commerce hub was central to the theme of the series, and having currency just made telling stories about that a lot more convenient.
I don't think that's really accurate; the Ferengi were portrated as greedy merchants focused on profit starting fairly early in TNG without direct reference to currency (gold -- not the later "gold-pressed latinum" -- was mentioned, IIRC, as an item of interest, but not in any context which implied it was used as currency); I think gold-pressed latinum as introduced as a currency in DS9 because DS9's role as commerce hub was central to the theme of the series, and having currency just made telling stories about that a lot more convenient.