Earlier quoted context omitted.
Tell that to Southwest Airways. http://en.wikipedia.org/wiki/Southwest_Airlines#Hedging_fuel Shuffling money around is also useful for making public what would otherwise be private information. Greece can profess to the world how solvent they are, but the swap market tells a different story.
I said "most of what they do" rather than "all of what they do" because some of it coincidentally helps others. The ratio of parasitic behavior to useful is unfortunately growing, and hasn't stopped just because it caused an economic meltdown.
As a former professional poker player myself, it never would occur to me to denigrate the work of financiers or suggest that what they were doing was immoral. I was able to morally justify my occupation to myself.. and, as such, it is orders of magnitude easier to justify theirs.