There are laws on the books but they're not vigorously enforced. While many of the scams originate offshore, there are also many homegrown. There seems to be little incentive for law enforcement to track down arrest and prosecute the scammers. Penalties are not severe enough.
From a criminal's perspective, it's a business. When the rewards exceed the risks, it's profitable. A scammer can steal hundreds of thousands from some unsuspecting marks and if caught and convicted face a few years in prison. Not a bad return. Unlike an armed robbery, the prospect of physical harm coming to a scammer is virtually non existent Make the risks great enough and the crime rate will go down. No cushy prison cell with thre squares and cable TV. If tey're going to prison, they should earn their keep. Multiple year sentences making gravel out of boulders with a sledge hammer come to mind. Perhaps the Muslims with their "cut off a hand" penalty would be in order.