You provide some interesting information but I wasn't claiming that it was true (hence the supposedly), only that the US Gov likely thinks that it has a vested interest in fighting piracy.
The resources used to fight piracy could indeed be used to fight something else, but that the system as a whole hasn't gained is not a certainty. If they shifted resources from focusing on finding snails breaking speeding laws to piracy, then I don't see how everyone isn't technically better off.
Everything you say about the effects of cracking down on piracy are true. Indeed, not all pirates will purchase in lieu of not using at all, but some will. There is some gain there, whether it is substantial or not, nobody knows.
As for the shifting money from private sector to government. That is an economic concern, and while I'm sure the government would prefer economic growth, I doubt they are averse to shifting money their way in this manner.