The scam uses email, so there is a very low cost to send. Newspapers have estimated that good scammers can get a response rate of .1% to .2%, which is pretty low.
And some people have this expectation that they can get rich quickly with little work. I know people like that. So breaking a law in a way that doesn't appear to hurt anyone just helps convince those people that there is a good reason for being offered so much money for so little work.
And some people have this expectation that they can get rich quickly with little work. I know people like that. So breaking a law in a way that doesn't appear to hurt anyone just helps convince those people that there is a good reason for being offered so much money for so little work.