Humans are stil gready, they're just greedy for knowledge, creation, science. In 24th century, they don't care about having the latest Iphone.
See, I'm just not 'buying' that. There will always be things that people want, whether it's an iphone or the latest transporter installed in your living room. And unless resources are unlimited, there was to be a value put on the exchange of them. Likewise, someone still needs to do the grunt work of civilization, and those people surely aren't doing it to fulfill their hunger for knowledge.
I also think if they make humans too perfect, it makes the show boring. How many of us rolled our eyes when Picard made that statement about money? To me it was what was wrong with that episode, they tried to make the 24th century humans too far removed from us, which made them unrelatable and unrealistic.