Wiretapping for Good

So I was wondering: if the U.S. government has no problems wiretapping U.S. citizens in lieu of a legal warrant or even probable cause (as evidenced by the sweeping, impersonal way in which the NSA collects data), then why can't it stop organized crime overnight?

I mean, if we can snoop the ether at random hoping to catch even a glimpse into organizations that might not even exist or that might not be planning anything even mildly interesting, then why can't they turn their prodigious data collection efforts towards something that is known to exist and that performs tangible bad acts every day of the week?

Yes, that was a rhetorical question.